1. In a food processor, pulse the 2 1/2 cups of flour with the salt.
Add the butter and pulse until it is the size of small peas. Add the
egg yolk and ice water and pulse until the pastry is moistened.
Turn the pastry out onto a floured work surface and knead 2 or 3
times, just until smooth. Pat the pastry into 2 disks, wrap in
plastic and refrigerate until firm, about 20 minutes.
2. Preheat the oven to 375°. On a floured surface, roll 1 disk of the
pastry to a 12-inch round. Ease the pastry into a 10-inch fluted
tart pan with a removable bottom without stretching. Trim the
excess and use it to patch any holes. Refrigerate the tart shell for
10 minutes. Repeat with the remaining pastry.
3. Line the tart shells with foil and fill with dried beans. Bake the
tart shells for 30 minutes, until dry. Remove the foil and beans
and bake the crusts for about 15 minutes longer, until they are dry
and golden. Transfer the tart pans to 2 sturdy baking sheets.
4. In a skillet, cook the bacon over moderately high heat, stirring,
until crisp, 7 minutes. Drain the bacon, leaving 1 tablespoon of the
fat in the pan. Add the leeks and thyme to the skillet, season with
salt and white pepper and cook over moderate heat, stirring, until
the leeks are softened but not browned, about 5 minutes. Transfer
to a bowl and let cool. Stir in the bacon and cheese.
5. Divide the filling between the tart shells. In a bowl, whisk the
eggs with the egg yolks and heavy cream. Season lightly with salt
and white pepper. Pour the custard into the shells and bake for
30 minutes, rotating the sheet halfway through, until puffed.
Transfer the quiches to a rack and let cool for 15 minutes. Remove
the rings, cut the quiches into wedges and serve. —Grace Parisi