01 -
Combine the flour and salt in a large bowl. Add the cubed butter and, using a pastry cutter or your fingertips, cut the butter into the flour until the mixture resembles coarse sand. Add the water, one tablespoon at a time, mixing until the dough comes together without overmixing.
02 -
Turn the dough out onto a lightly floured surface and knead until just formed into a ball. Transfer it to parchment paper, flatten into a disk, cover with another sheet of parchment, and roll into a 10-inch circle. Carefully place the dough in a 10-inch tart pan and chill for 30 minutes.
03 -
Preheat the oven to 425°F (220°C). Pierce the bottom of the crust with a fork. Line it with parchment paper and fill with pie weights or dried beans. Bake for 10 minutes, remove the weights and paper, and set the crust aside.
04 -
In a large skillet over medium heat, cook the diced bacon until crisp, about 5 minutes. Use a slotted spoon to transfer the bacon to a plate. Discard all but 1 teaspoon of the bacon fat.
05 -
Add the butter to the skillet and, once melted, stir in the shallot. Cook until translucent, about 2 minutes. Add the leeks and coat with the fat. Pour in the white wine, partially cover, and cook, stirring occasionally, until soft, about 8 to 10 minutes. Season with salt, pepper, and nutmeg.
06 -
Return the bacon to the skillet. Stir in the flour and cook while stirring for 2 minutes. Add the milk and continue stirring until thickened. Stir in the creme fraiche until fully incorporated. Remove from heat and let cool slightly before mixing in the eggs and 1 cup of Gruyere cheese.
07 -
Pour the filling mixture into the pre-baked crust. Sprinkle the remaining Gruyere cheese evenly over the top.
08 -
Bake at 425°F (220°C) until set and golden brown, about 35 to 40 minutes. Allow to cool for at least 30 minutes before serving warm or at room temperature.