Alsace onion tart

Gabriel Kreuther takes the humble onion tart – a classic in the northern French region of Alsace where he grew up – and gives it his own special treatment.

Course: Main Course

Cuisine: French

Keyword: Gabriel Kreuther, French tart recipe, Alsace Onion Tart

Author: Gabriel Kreuther

Ingredients

For the dough

2 cups 250 g all-purpose flour
1 stick + 1 tbsp 130 g cold butter, diced
Salt
75 ml cold water

For the filling

3 ½ to 4 lbs 1.75 kg onions
Salt
4 oz 125 g applewood-smoked slab bacon, cut into thin strips
4 eggs
1 cup 240 ml heavy (double) cream
200 ml milk
2 tbsp chopped parsley
50 grinds pepper or to taste
30 gratings nutmeg or to taste
3 oz 100 g grated Gruyère (or enough to sprinkle liberally over the tart)

Instructions

To make the dough

Blend together the flour, butter, and salt in a mixing bowl with your fingertips just until the mixture resembles coarse meal with some roughly pea-sized lumps.
Add most of the 1/3 cup (75 ml) of water and mix until the dough comes together, adding more water as needed.
Work the dough until it is smooth and not sticky.
Wrap in plastic and let it rest in the refrigerator for 30 minutes while you prepare the filling.

To make the filling

Put about threequarters of the onions in a steamer for 1 hour or until completely tender; you can also wrap them in foil and roast them at 350°F (175°C) for the same time, or until tender.
Purée them in a blender until they’re completely smooth.

Onion tart

With the other onions, halve each one lengthwise. Take one half and put it on your cutting board. Make a slice through the middle just to the core so that it stays together and your slices are short. Slice the onion as thinly as possible, starting at the top and moving down to the core. Repeat with the remaining onions. This can be done on a mandoline as well. Put the sliced onions into a bowl, sprinkle with 1 teaspoon of salt, and toss to distribute the salt.
Preheat your oven to 325°F (175°C, Gas Mark 4).
When the dough has rested, roll it out and line an 11 or 12 in (28 or 30.5 cm) tart pan with it. Poke holes in the bottom with a fork. Fill the tart with beans on parchment or foil, or use pie weights to hold the dough down, and blind bake it for 20 minutes.
Sauté the bacon over medium heat until cooked, lightly coloured but not crispy. Remove the pan from the heat and allow the bacon pieces to cool in the pan.
Raise oven temperature to 375°F (190°C, Gas Mark 5).
Beat the eggs in a mixing bowl. Whisk in the cream, milk, onion purée, sliced onion, 1 tablespoon salt, the parsley, and the pepper and nutmeg to taste.
Pour the onion mixture into the tart shell. Sprinkle the grated cheese over the top. Sprinkle the bacon evenly over the top (feel free to drizzle any rendered bacon fat over the tart as well) and bake the tart for about 40 minutes, until just set (it should jiggle but not appear liquidy). Allow it to cool for 15 minutes before serving warm, or allow it to cool completely to serve at room temperature. This will keep well wrapped in the fridge for several days.