104min 4 ppl
Alsatian Onion Tart
151 minutes
4 people
Hardover 60 min or 12+ steps
151 min · 13 steps
Hard: over 60 min or 12+ steps
680 kcalper person
Protein 14g
Carbs 52g
Fats 46g
About this dish
Slow-caramelised onions cooked in butter until jammy and golden — not just softened — set the standard for an Alsatian onion tart. A custard of crème fraîche and egg yolks, seasoned with freshly grated nutmeg, sets to a silky, barely-trembling fill inside a buttery shortcrust shell blind-baked until truly crisp.
Allergy Info
Dairy, Gluten, Eggs
Diet Info
Vegetarian
Ingredients
Fresh Produce
- White or yellow onionspeeled and thinly sliced into half-moons1.2 kg
- Fresh thyme leaves1 tbsp
Dairy & Eggs
- Unsalted butter80 g
- Egg yolks3 large
- Whole egg1 large
- Full-fat crème fraîche200 g
- Unsalted buttercubed and ice-cold100 g
- Egg yolk1 large
Dried Goods
- Caster sugar1 tsp
- Plain flourcold200 g
Spices & Seasonings
- Fine sea saltdivided1 tsp
- Freshly grated nutmeg¼ tsp
- White pepperfreshly ground¼ tsp
- Fine sea salt½ tsp
Oils & Condiments
- Dry Alsatian Riesling or dry white wine2 tbsp
Other
- Ice-cold water2-3 tbsp
Utensils
- Tart tin
- Rolling pin
- Wide heavy-based saucepan
- Mixing bowl
- Whisk
Method
1
Make the pastry: combine the flour and salt in a bowl. Rub in the cold butter with your fingertips until the mixture resembles coarse breadcrumbs with some pea-sized pieces remaining. Add the egg yolk and 2 tablespoons of the ice-cold water and bring together into a shaggy dough, adding the third tablespoon only if needed. Press into a flat disc and wrap.
Approx. 10 minutes
2
Refrigerate the pastry disc for at least 1 hour, or overnight.
Approx. 2 minutes
3
Melt the butter in a wide, heavy-based saucepan or casserole over medium-low heat. Add the onions, ½ teaspoon salt and the sugar. Stir to coat, then cook uncovered, stirring every 5–7 minutes, for 45–50 minutes until deeply golden, jammy and reduced to roughly a quarter of their original volume — they should smell sweet and nutty, not sharp.
Approx. 48 minutes
4
Add the Riesling to the pan and stir, scraping up any fond from the base. Cook for 2 minutes until the wine has fully evaporated.
Approx. 2 minutes
5
Remove from heat and allow the onions to cool to room temperature.
Approx. 3 minutes
6
Preheat the oven to 200°C, or 180°C for a fan oven, or gas mark 6. Roll the chilled pastry on a lightly floured surface to a 3mm circle large enough to line a 23cm loose-bottomed tart tin. Press into the tin, trim the overhang to 1cm and fold it back inside to reinforce the sides. Prick the base all over with a fork.
Approx. 15 minutes
7
Line the pastry shell with baking parchment and fill with baking beans or uncooked rice.
Approx. 3 minutes
8
Blind-bake for 18 minutes until the sides are set and pale gold.
Approx. 18 minutes
9
Remove the baking beans and parchment. Return the tin to the oven and bake for a further 8 minutes until the base is dry, pale biscuit-coloured and no longer raw-looking. Remove and reduce the oven temperature to 170°C, or 150°C for a fan oven, or gas mark 3.
Approx. 8 minutes
10
Whisk together the egg yolks, whole egg, crème fraîche, remaining ½ teaspoon salt, white pepper and nutmeg in a bowl until smooth and homogeneous.
Approx. 5 minutes
11
Spread the cooled caramelised onions evenly over the blind-baked tart shell. Scatter the thyme leaves over the onions. Pour the custard mixture slowly and evenly over the top.
Approx. 5 minutes
12
Bake at 170°C for 28–32 minutes until the custard is just set at the edges with a slight tremble in the very centre, and the surface is lightly golden.
Approx. 30 minutes
13
Rest the tart in the tin for 10 minutes before slicing.
Approx. 2 minutes
