2 sticks (1/2 pound) unsalted butter, cut into 1/2-inch pieces and chilled
1 large egg yolk
6 tablespoons ice water
Preheat the oven to 375°. Let the dough stand at room temperature for 10 minutes. On a lightly floured work surface, roll out each disk to a 12-inch round about 3/8 inch thick. Fit the dough into two 10-inch fluted tart pans with removable bottoms. Trim off any excess dough. Line each shell with foil and fill with pie weights or dried beans.
Bake the shells for 25 minutes, or until just set and slightly dry. Remove the foil and weights and bake the shells for 5 to 10 minutes longer, until dry and lightly golden. Transfer to racks; let cool.
The shells can be stored at room temperature for 2 days.