In a large bowl, whisk together the flour, powdered sugar and salt until well blended. Work in the butter and egg yolk, with a pastry blender or with your fingertips, until pea sized pieces are formed. Add ice water one tablespoon (15ml) at a time until the dough comes together.
Form the dough into a disk. Wrap in plastic wrap and chill in the refrigerator for at least one hour or up to overnight.
On a lightly floured surface, roll the dough to a scant 1/4-inch thickness. Cut the dough into six 5-inch rounds.
Press the rounds into six 4-inch or 4 1/4-inch tart pans. Dock the bottoms of the tart crusts with a fork. Freeze for 30 minutes.
Meanwhile, preheat oven to 375ºF (190ºC). Place the tart pans on a large baking sheet. Line the tart shells with 6-inch parchment rounds. Fill with pie weights. (You can use dried beans or rice if you don't have pie weights.)
Bake the tart shells for 12 minutes. Remove the parchment paper and pie weights. Continue baking until the tart shells are light golden brown, about 4-6 more minutes.