French Onion Tart

Name: French Onion Tart
Total time: 1 h 47 min
Yield: 4 servings
Cuisine: french
Ingredients: 200 g Plain flour; 0.25 tsp Fine salt; 100 g Unsalted butter; 30 ml Water; 10 g Unsalted butter; 1,000 g Yellow onion; 50 g Unsalted butter; 0.5 tsp Fine salt; 2 piece Bay leaf; 4 sprig Fresh thyme; 3 piece Egg; 100 ml Whole milk; 200 ml Double cream; 1 pinch Ground black pepper; 1 pinch Ground nutmeg; 80 g Gruyère; 10 g Plain flour, for dusting

1 hr 47 min · 16 min active · makes 4 tarts · ~1.95 kg · Medium

Caramelised yellow onions, cooked slowly with bay and thyme, set in a cream custard under a golden Gruyère top in a buttery pastry shell.

See more →

French Onion Tart

Caramelised yellow onions, cooked slowly with bay and thyme, set in a cream custard under a golden Gruyère top in a buttery pastry shell.

See more →

TOTAL TIME

1 hr 47 min

ACTIVE TIME

16 min

QUANTITY

4 tarts · ~1.95 kg

DIFFICULTY

Medium

CUISINE

—

Who’s eating

People here are for suitability — allergies, preferences and what to watch for. Portion sizing is off for this recipe.

Portions & fullness

Ingredients0/13

Tools0/20

Ingredients

0/13 gathered · 4 servings

210g

0.75tsp

160g

30ml

1,000g

2piece

4sprig

3piece

100ml

200ml

1pinch

80g

#	Quantity	Notes	State
1	210g	—	—
2	0.75tsp	—	—
3	160g	—	—
4	30ml	—	—
5	1,000g	—	—
6	2piece	—	—
7	4sprig	—	—
8	3piece	—	—
9	100ml	—	—
10	200ml	—	—
11	1pinch	—	—
12	1pinch	—	—
13	80g	—	—

Tools

20 items

Serveware

1 item

Procedure

49 steps

1 of 49

Tip the flour into a large mixing bowl.

Plain flour · 200 g

⏱ 10s

ResultPlain flour

2 of 49

Add the salt to the flour.

Fine salt · 0.25 tsp

⏱ 5s

ResultPlain flour and fine salt

3 of 49

Add the cold butter, cut into small cubes, to the bowl.

Unsalted butter · 100 g

⏱ 10s

ResultPlain flour and fine salt and unsalted butter

4 of 49

Rub the butter into the flour with your fingertips, lifting and crumbling, until the mixture resembles fine breadcrumbs with no visible lumps of butter.

⏱ 2 min

ResultShortcrust crumbs

5 of 49

Drizzle the cold water over the crumbs.

Water · 30 ml

⏱ 5s

ResultShortcrust crumbs and water

6 of 49

Bring the dough together with your hands, pressing and folding just until it holds — stop as soon as it is smooth and avoid overworking it.

⏱ 30s

ResultShortcrust pastry dough

7 of 49

Pat the dough into a flat disc and wrap it tightly in cling film.

⏱ 10s

ResultWrapped shortcrust pastry dough

8 of 49

Place the wrapped dough in the refrigerator.

⏱ 10s

ResultWrapped shortcrust pastry dough

9 of 49

Leave the dough to rest in the refrigerator for 30 minutes until firm and relaxed.

⏱ 30 min

ResultChilled shortcrust pastry dough

10 of 49

Remove the dough from the refrigerator.

⏱ 5s

ResultChilled shortcrust pastry doughused in step 13

11 of 49

Preheat the oven to 190 °C.

190°C

⏱ 10 min

12 of 49

Rub the tart tin all over with a little butter to grease it thoroughly.

Unsalted butter · 10 g

⏱ 20s

ResultUnsalted butter

13 of 49

Unwrap the dough onto a lightly floured surface and roll it out from the centre in all directions until it is a round about 3 mm thick and large enough to line a 23 cm tart tin with overhang.

Plain flour · 10 gChilled shortcrust pastry dough · step 10

⏱ 1 min

ResultRolled pastry sheet

14 of 49

Drape the pastry over the rolling pin, lift it over the tart tin and unroll it gently, then press it into the base and sides without stretching, letting the excess hang over the edge.

Rolled pastry sheet · step 13

⏱ 30s

ResultPastry-lined case

15 of 49

Run a knife across the top of the tin to trim away the overhanging pastry cleanly.

⏱ 20s

ResultTrimmed pastry case

16 of 49

Prick the base all over with a fork to prevent it from puffing up during blind baking.

⏱ 20s

ResultPricked pastry case

17 of 49

Cut a sheet of baking paper larger than the tin, scrunch it up, then open it out and press it into the pastry case.

⏱ 20s

18 of 49

Pour in baking beans to fill the lined pastry case.

⏱ 10s

ResultPricked pastry case and fine salt

19 of 49

Place the tart tin in the oven.

⏱ 10s

ResultPricked pastry case and fine salt

20 of 49

Bake the pastry case for 15 minutes until the sides are set and just beginning to colour.

190°C

⏱ 15 min

ResultBlind-baked pastry case

21 of 49

Lift the tart tin out of the oven using oven gloves and set it on a heatproof surface.

⏱ 15s

ResultBlind-baked pastry case

22 of 49

Lift out the baking paper and baking beans carefully, holding the paper by its edges, leaving the pastry case in the tin.

Blind-baked pastry case · step 21

⏱ 20s

ResultPricked pastry case

23 of 49

Return the empty pastry case in its tin to the oven.

Pricked pastry case · step 22

⏱ 10s

ResultPricked pastry case

24 of 49

Bake for a further 8 minutes until the base is dry, pale gold and cooked through.

190°C

⏱ 8 min

ResultGolden pastry case

25 of 49

Remove the tart tin from the oven using oven gloves and set aside while you make the filling.

⏱ 10s

ResultGolden pastry case

26 of 49

Peel the yellow onion

Yellow onion · 1,000 g

⏱ 1 min 30s

ResultPeeled yellow onion

27 of 49

Halve each peeled onion through the root, then slice them as thinly and evenly as possible into half-moons.

Peeled yellow onion · step 26

⏱ 2 min

ResultSliced yellow onionused in step 30

28 of 49

Put the butter into a large frying pan.

Unsalted butter · 50 g

⏱ 5s

ResultUnsalted butter

29 of 49

Set the pan over a medium-low heat and let the butter melt completely without colouring.

⏱ 1 min

ResultMelted butter

30 of 49

Tip all the sliced onions into the pan and stir to coat them in the butter.

Sliced yellow onion · step 27

⏱ 15s

ResultSliced yellow onion and melted butter

31 of 49

Season the onions with the salt to help them release their liquid.

Fine salt · 0.5 tsp

⏱ 5s

ResultSliced yellow onion and melted butter and fine salt

32 of 49

Add the bay leaves to the onions.

Bay leaf · 2 piece

⏱ 5s

ResultSliced yellow onion and melted butter mixture

33 of 49

Tuck the thyme sprigs among the onions.

Fresh thyme · 4 sprig

⏱ 5s

ResultSliced yellow onion and melted butter mixture

34 of 49

Cook over a low heat, stirring every 5–10 minutes, for about 50 minutes until the onions are very soft, deeply golden and sweet — do not rush this.

⏱ 50 min

ResultCaramelised onions

35 of 49

Use tongs to lift out and discard the thyme sprigs and bay leaves, leaving the caramelised onions in the pan.

⏱ 15s

ResultCaramelised onions with bay leavesused in step 43

36 of 49

Crack the eggs into a medium bowl, discarding the shells.

Egg · 3 piece

⏱ 15s

ResultEgg

37 of 49

Add the whole milk to the bowl with the eggs.

Whole milk · 100 ml

⏱ 5s

ResultEgg and whole milk

38 of 49

Add the double cream to the bowl.

Double cream · 200 ml

⏱ 5s

ResultEgg and whole milk and double cream

39 of 49

Add the black pepper.

Ground black pepper · 1 pinch

⏱ 5s

ResultEgg mixture

40 of 49

Add the nutmeg.

Ground nutmeg · 1 pinch

⏱ 5s

ResultEgg mixture

41 of 49

Whisk the eggs, cream and spices together until smooth and evenly combined.

⏱ 30s

ResultCustard mixtureused in step 44

42 of 49

Grate the Gruyère on the coarse side of a grater into a small bowl.

Gruyère · 80 g

⏱ 1 min

ResultGrated Gruyèreused in step 45

43 of 49

Spoon the caramelised onions into the pastry case and spread them in an even layer.

Caramelised onions with bay leaves · step 35

⏱ 20s

ResultGolden pastry case and caramelised onions with bay leaves

44 of 49

Pour the custard mixture slowly over the onions, letting it settle into every gap.

Custard mixture · step 41

⏱ 15s

ResultCustard mixture and golden pastry case and caramelised onions with bay leaves

45 of 49

Scatter the grated Gruyère evenly over the surface of the filled tart.

Grated Gruyère · step 42

⏱ 15s

ResultAssembled french onion tart

46 of 49

Carefully slide the filled tart tin into the oven.

⏱ 10s

ResultAssembled french onion tart

47 of 49

Bake for 30 minutes until the custard is just set with a slight wobble in the centre and the Gruyère is golden and bubbling.

190°C

⏱ 30 min

ResultBaked french onion tart

48 of 49

Remove the tart from the oven using oven gloves and place it on a wire rack.

⏱ 10s

ResultBaked french onion tart

49 of 49

Leave the tart to cool and settle in its tin for 10 minutes before slicing — this helps the custard firm up and makes it easier to cut cleanly.

⏱ 10 min

ResultRested french onion tart

Total Time1 hr 47 min

#	Product	Tool	Action
1	200 g		Tip the flour into a large mixing bowl.⏱ 10sResultPlain flour
2	0.25 tsp		Add the salt to the flour.⏱ 5sResultPlain flour and fine salt
3	100 g		Add the cold butter, cut into small cubes, to the bowl.⏱ 10sResultPlain flour and fine salt and unsalted butter
4	—		Rub the butter into the flour with your fingertips, lifting and crumbling, until the mixture resembles fine breadcrumbs with no visible lumps of butter.⏱ 2 minResultShortcrust crumbs
5	30 ml		Drizzle the cold water over the crumbs.⏱ 5sResultShortcrust crumbs and water
6	—		Bring the dough together with your hands, pressing and folding just until it holds — stop as soon as it is smooth and avoid overworking it.⏱ 30sResultShortcrust pastry dough
7	—		Pat the dough into a flat disc and wrap it tightly in cling film.⏱ 10sResultWrapped shortcrust pastry dough
8	—		Place the wrapped dough in the refrigerator.⏱ 10sResultWrapped shortcrust pastry dough
9	—		Leave the dough to rest in the refrigerator for 30 minutes until firm and relaxed.⏱ 30 minResultChilled shortcrust pastry dough
10	—		Remove the dough from the refrigerator.⏱ 5sResultChilled shortcrust pastry doughused in step 13
11	—	190°C	Preheat the oven to 190 °C.⏱ 10 min
12	10 g		Rub the tart tin all over with a little butter to grease it thoroughly.⏱ 20sResultUnsalted butter
13	10 g		Unwrap the dough onto a lightly floured surface and roll it out from the centre in all directions until it is a round about 3 mm thick and large enough to line a 23 cm tart tin with overhang.⏱ 1 minResultRolled pastry sheet
13	Chilled shortcrust pastry doughstep 10
14	Rolled pastry sheetstep 13		Drape the pastry over the rolling pin, lift it over the tart tin and unroll it gently, then press it into the base and sides without stretching, letting the excess hang over the edge.⏱ 30sResultPastry-lined case
15	—		Run a knife across the top of the tin to trim away the overhanging pastry cleanly.⏱ 20sResultTrimmed pastry case
16	—		Prick the base all over with a fork to prevent it from puffing up during blind baking.⏱ 20sResultPricked pastry case
17	—		Cut a sheet of baking paper larger than the tin, scrunch it up, then open it out and press it into the pastry case.⏱ 20s
18	—		Pour in baking beans to fill the lined pastry case.⏱ 10sResultPricked pastry case and fine salt
19	—		Place the tart tin in the oven.⏱ 10sResultPricked pastry case and fine salt
20	—	190°C	Bake the pastry case for 15 minutes until the sides are set and just beginning to colour.⏱ 15 minResultBlind-baked pastry case
21	—		Lift the tart tin out of the oven using oven gloves and set it on a heatproof surface.⏱ 15sResultBlind-baked pastry case
22	Blind-baked pastry casestep 21		Lift out the baking paper and baking beans carefully, holding the paper by its edges, leaving the pastry case in the tin.⏱ 20sResultPricked pastry case
23	Pricked pastry casestep 22		Return the empty pastry case in its tin to the oven.⏱ 10sResultPricked pastry case
24	—	190°C	Bake for a further 8 minutes until the base is dry, pale gold and cooked through.⏱ 8 minResultGolden pastry case
25	—		Remove the tart tin from the oven using oven gloves and set aside while you make the filling.⏱ 10sResultGolden pastry case
26	1,000 g		Peel the yellow onion⏱ 1 min 30sResultPeeled yellow onion
27	Peeled yellow onionstep 26		Halve each peeled onion through the root, then slice them as thinly and evenly as possible into half-moons.⏱ 2 minResultSliced yellow onionused in step 30
28	50 g		Put the butter into a large frying pan.⏱ 5sResultUnsalted butter
29	—		Set the pan over a medium-low heat and let the butter melt completely without colouring.⏱ 1 minResultMelted butter
30	Sliced yellow onionstep 27		Tip all the sliced onions into the pan and stir to coat them in the butter.⏱ 15sResultSliced yellow onion and melted butter
31	0.5 tsp		Season the onions with the salt to help them release their liquid.⏱ 5sResultSliced yellow onion and melted butter and fine salt
32	2 piece		Add the bay leaves to the onions.⏱ 5sResultSliced yellow onion and melted butter mixture
33	4 sprig		Tuck the thyme sprigs among the onions.⏱ 5sResultSliced yellow onion and melted butter mixture
34	—		Cook over a low heat, stirring every 5–10 minutes, for about 50 minutes until the onions are very soft, deeply golden and sweet — do not rush this.⏱ 50 minResultCaramelised onions
35	—		Use tongs to lift out and discard the thyme sprigs and bay leaves, leaving the caramelised onions in the pan.⏱ 15sResultCaramelised onions with bay leavesused in step 43
36	3 piece		Crack the eggs into a medium bowl, discarding the shells.⏱ 15sResultEgg
37	100 ml		Add the whole milk to the bowl with the eggs.⏱ 5sResultEgg and whole milk
38	200 ml		Add the double cream to the bowl.⏱ 5sResultEgg and whole milk and double cream
39	1 pinch		Add the black pepper.⏱ 5sResultEgg mixture
40	1 pinch		Add the nutmeg.⏱ 5sResultEgg mixture
41	—		Whisk the eggs, cream and spices together until smooth and evenly combined.⏱ 30sResultCustard mixtureused in step 44
42	80 g		Grate the Gruyère on the coarse side of a grater into a small bowl.⏱ 1 minResultGrated Gruyèreused in step 45
43	Caramelised onions with bay leavesstep 35		Spoon the caramelised onions into the pastry case and spread them in an even layer.⏱ 20sResultGolden pastry case and caramelised onions with bay leaves
44	Custard mixturestep 41		Pour the custard mixture slowly over the onions, letting it settle into every gap.⏱ 15sResultCustard mixture and golden pastry case and caramelised onions with bay leaves
45	Grated Gruyèrestep 42		Scatter the grated Gruyère evenly over the surface of the filled tart.⏱ 15sResultAssembled french onion tart
46	—		Carefully slide the filled tart tin into the oven.⏱ 10sResultAssembled french onion tart
47	—	190°C	Bake for 30 minutes until the custard is just set with a slight wobble in the centre and the Gruyère is golden and bubbling.⏱ 30 minResultBaked french onion tart
48	—		Remove the tart from the oven using oven gloves and place it on a wire rack.⏱ 10sResultBaked french onion tart
49	—		Leave the tart to cool and settle in its tin for 10 minutes before slicing — this helps the custard firm up and makes it easier to cut cleanly.⏱ 10 minResultRested french onion tart
Total Time			1 hr 47 min

Serving

Slide the tart from the tin onto a large serving plate, cut into 4 wedges and bring straight to the table.

Nutrition

per serving

Estimated · pre-cooking · 100% ingredients covered

Nutrient	Per serving
	954kcal
	21g
	62g
	37g
	66g
	14g
	6g
	693mg

Ingredients0/13

Tools0/20

Recipe

French Onion Tart

Caramelised yellow onions, cooked slowly with bay and thyme, set in a cream custard under a golden Gruyère top in a buttery pastry shell.

What you’ll doYou will make shortcrust pastry, rest it, then blind bake it. While it cools, you will cook sliced onions slowly in butter with bay and thyme for about 50 minutes until deeply golden and sweet—this cannot be rushed. You will whisk eggs, milk, cream and spices into a custard, spread the onions in the pastry case, pour the custard over them and scatter the grated Gruyère on top, then bake until the centre has a slight wobble and the cheese is bubbling. The tart must rest for 10 minutes before turning out.

Serves4

Total1 hr 47 min

LevelMedium

Ingredients

Plain flour210 g
Fine salt0.75 tsp
Unsalted butter160 g
Water30 ml
Yellow onion1,000 g
Bay leaf2 piece
Fresh thyme4 sprig
Egg3 piece
Whole milk100 ml
Double cream200 ml
Ground black pepper1 pinch
Ground nutmeg1 pinch
Gruyère80 g

Tools

Kitchen counterTongsRolling pinSmall bowlLarge mixing bowlOvenLarge frying panChef's knifeMedium bowlCling filmWhiskWooden spoonRefrigeratorLarge serving plateGraterBaking paperForkTart tinOven gloveChopping board

Method

Tip the flour into a large mixing bowl.

10sLarge mixing bowlPlain flour · 200 g

Add the salt to the flour.

5sLarge mixing bowlFine salt · 0.25 tsp

Add the cold butter, cut into small cubes, to the bowl.

10sLarge mixing bowlUnsalted butter · 100 g

Rub the butter into the flour with your fingertips, lifting and crumbling, until the mixture resembles fine breadcrumbs with no visible lumps of butter.

2 minLarge mixing bowl

Drizzle the cold water over the crumbs.

5sLarge mixing bowlWater · 30 ml

Bring the dough together with your hands, pressing and folding just until it holds — stop as soon as it is smooth and avoid overworking it.

30sLarge mixing bowl

Pat the dough into a flat disc and wrap it tightly in cling film.

10sLarge mixing bowl, Cling film

Place the wrapped dough in the refrigerator.

10sLarge mixing bowl, Refrigerator

Leave the dough to rest in the refrigerator for 30 minutes until firm and relaxed.

30 minLarge mixing bowl

Remove the dough from the refrigerator.

Result · Chilled shortcrust pastry dough · used in step 13

5sLarge mixing bowl, Refrigerator

Preheat the oven to 190 °C.

190°C10 minOven

Rub the tart tin all over with a little butter to grease it thoroughly.

20sTart tinUnsalted butter · 10 g

Unwrap the dough onto a lightly floured surface and roll it out from the centre in all directions until it is a round about 3 mm thick and large enough to line a 23 cm tart tin with overhang.

1 minKitchen counter, Rolling pinPlain flour · 10 g

Drape the pastry over the rolling pin, lift it over the tart tin and unroll it gently, then press it into the base and sides without stretching, letting the excess hang over the edge.

30sTart tin, Rolling pinRolled pastry sheet · step 13

Run a knife across the top of the tin to trim away the overhanging pastry cleanly.

20sTart tin, Chefs knife

Prick the base all over with a fork to prevent it from puffing up during blind baking.

20sTart tin, Fork

Cut a sheet of baking paper larger than the tin, scrunch it up, then open it out and press it into the pastry case.

20sTart tin, Baking paper

Pour in baking beans to fill the lined pastry case.

10sTart tin

Place the tart tin in the oven.

10sTart tin, Oven, Oven glove

Bake the pastry case for 15 minutes until the sides are set and just beginning to colour.

190°C15 minTart tin, Oven

Lift the tart tin out of the oven using oven gloves and set it on a heatproof surface.

15sTart tin, Oven, Oven glove

Lift out the baking paper and baking beans carefully, holding the paper by its edges, leaving the pastry case in the tin.

20sKitchen counterBlind-baked pastry case · step 21

Return the empty pastry case in its tin to the oven.

10sTart tin, Oven, Oven glovePricked pastry case · step 22

Bake for a further 8 minutes until the base is dry, pale gold and cooked through.

190°C8 minTart tin, Oven

Remove the tart tin from the oven using oven gloves and set aside while you make the filling.

10sTart tin, Oven, Oven glove

Peel the yellow onion

1 min 30sChopping board, Chefs knifeYellow onion · 1,000 g

Halve each peeled onion through the root, then slice them as thinly and evenly as possible into half-moons.

Result · Sliced yellow onion · used in step 30

2 minChopping board, Chefs knifePeeled yellow onion · step 26

Put the butter into a large frying pan.

5sLarge frying panUnsalted butter · 50 g

Set the pan over a medium-low heat and let the butter melt completely without colouring.

1 minLarge frying pan

Tip all the sliced onions into the pan and stir to coat them in the butter.

15sLarge frying panSliced yellow onion · step 27

Season the onions with the salt to help them release their liquid.

5sLarge frying panFine salt · 0.5 tsp

Add the bay leaves to the onions.

5sLarge frying panBay leaf · 2 piece

Tuck the thyme sprigs among the onions.

5sLarge frying panFresh thyme · 4 sprig

Cook over a low heat, stirring every 5–10 minutes, for about 50 minutes until the onions are very soft, deeply golden and sweet — do not rush this.

50 minLarge frying pan, Wooden spoon

Use tongs to lift out and discard the thyme sprigs and bay leaves, leaving the caramelised onions in the pan.

Result · Caramelised onions with bay leaves · used in step 43

15sLarge frying pan, Tongs

Crack the eggs into a medium bowl, discarding the shells.

15sMedium bowlEgg · 3 piece

Add the whole milk to the bowl with the eggs.

5sMedium bowlWhole milk · 100 ml

Add the double cream to the bowl.

5sMedium bowlDouble cream · 200 ml

Add the black pepper.

5sMedium bowlGround black pepper · 1 pinch

Add the nutmeg.

5sMedium bowlGround nutmeg · 1 pinch

Whisk the eggs, cream and spices together until smooth and evenly combined.

Result · Custard mixture · used in step 44

30sMedium bowl, Whisk

Grate the Gruyère on the coarse side of a grater into a small bowl.

Result · Grated Gruyère · used in step 45

1 minSmall bowl, GraterGruyère · 80 g

Spoon the caramelised onions into the pastry case and spread them in an even layer.

20sTart tinCaramelised onions with bay leaves · step 35

Pour the custard mixture slowly over the onions, letting it settle into every gap.

15sTart tinCustard mixture · step 41

Scatter the grated Gruyère evenly over the surface of the filled tart.

15sTart tinGrated Gruyère · step 42

Carefully slide the filled tart tin into the oven.

10sTart tin, Oven, Oven glove

Bake for 30 minutes until the custard is just set with a slight wobble in the centre and the Gruyère is golden and bubbling.

190°C30 minTart tin, Oven

Remove the tart from the oven using oven gloves and place it on a wire rack.

10sTart tin, Oven, Oven glove

Leave the tart to cool and settle in its tin for 10 minutes before slicing — this helps the custard firm up and makes it easier to cut cleanly.

10 minTart tin

Slide the tart from the tin onto a large serving plate, cut into 4 wedges and bring straight to the table.

Result · Rested french onion tart

20sLarge serving plateRested french onion tart · step 49

Printed 11 October 2026