THE RESULT: Mealy crust.THE FIX: To get the quintessential flakiness that defines a perfect piecrust, the dough has to stay cold. Here’s how it works: Pie dough recipes usually call for the fat (butter or shortening) to be cut into the dry ingredients using a pastry blender or two knives, which distributes small bits of fat coated in dry ingredients throughout the mixture. While the crust bakes, those bits of fat melt, giving off steam and creating flaky layers. When the dough gets warm before making it to the oven, the bits start melding together too soon, altering the consistency of the crust and preventing the formation of the flaky layers. Once the pie dough is rolled out, chill it for 30 minutes before adding the filling.