Leek Quiche (French Quiche aux Poireaux)

Steps

1. Make the dough: in a bowl, mix 220 g of flour with 1/2 teaspoon of salt. Add 110 g of very cold butter cut into 1 cm (1/2 inch) cubes and rub it between your fingertips until the mixture looks like coarse sand with pea-size flakes of butter still visible. Drizzle in 50 ml of cold water while stirring with a fork, and stop as soon as the dough holds together when squeezed in your hand.
2. Gather the dough into a ball without kneading, then smear it 2 times under the heel of your hand on the counter to bind the butter and flour without making it elastic. Flatten it into a disk 2 cm (3/4 inch) thick, wrap it, and chill for 30 minutes.
3. Meanwhile, trim the roots and dark green tops from the leeks, split the stalks lengthwise, and rinse them under running water, fanning the layers to flush out any grit. Slice them into 5 mm (1/4 inch) half-moons.
4. Melt 30 g of butter in a large sauté pan over medium heat, then turn it down a notch. Add the leeks, 1/2 teaspoon of salt, and 50 ml of water, cover, and let them soften for 15 minutes, stirring now and then: they should turn supple and translucent with no color at all. Uncover and cook 5 minutes more to evaporate the remaining juice.
5. Tip the leeks into a colander and press them firmly with the back of a spoon to squeeze out all the liquid, then let them cool slightly. A custard flooded with leek juice will not set and soaks the crust.
6. Heat the oven to 375°F (190°C). Roll the dough on a floured counter to 3 mm (1/8 inch) thick and line a 26 cm (10 inch) deep tart pan, letting the dough drop into the corners without stretching it. Trim the excess, prick the base with a fork, and chill the pan for 15 minutes: very cold dough shrinks far less.
7. Blind bake: cover the dough with a round of parchment, fill it to the rim with pie weights or dried beans, and bake for 15 minutes. Remove the parchment and weights and bake 8 to 10 minutes more, until the base is dry, matte, and golden. Turn the oven down to 350°F (180°C).
8. Make the custard: in a pitcher, whisk 4 whole eggs and 1 yolk with 200 ml of cream, 150 ml of milk, 1/2 teaspoon of salt, the pepper, and 2 pinches of nutmeg, just until smooth without making it foamy.
9. Scatter half the Emmental over the still-warm crust, spread the leeks on top, then pour in the custard gently. Sprinkle with the rest of the cheese. Bake at 350°F (180°C) for 35 to 40 minutes, until the top is browned in spots and the center still wobbles a little when you nudge the pan.
10. Let the quiche rest for 15 minutes before unmolding and slicing: it finishes cooking out of the oven and the slices hold neat edges.