Before you start mixing your dough, make sure all your ingredients are icy cold. You might even want to pop your bowl into the freezer to chill it down. Why? Most pastry recipes call for cutting in fat—whether you're using butter, lard, or shortening—to a flour mixture. When you do that, you want to make sure everything stays cool enough that the finished pastry is flecked with distinct, un-melted nuggets of fat. To be extra careful, some bakers even use the big holes on a box grater to grate frozen butter or lard into flour. The reason is simple: when those cold nuggets of fat hit the heat of the oven, they expand to create pockets of steam. And those pockets are the secret to achieving every pie baker's goal: flakiness!
Drizzle, Don't Pour
When a pastry recipe calls for adding water or other liquids, always add drop by drop and use the minimum called for. (You can always add more if the pastry looks dry, but you can't take it away!) Water is one of the things that jump starts gluten formation in dough and using too much can result in a tough crust. Another clever trick: try replacing a bit of the water in a recipe with vodka, lemon juice, or vinegar. Why? Acid helps slow down the formation of gluten, so it moistens dough while still keeping it tender.
Use a Light Touch
There are a few reasons it's important not to overwork pastry dough. One: the heat of your hands can melt those important nuggets of fat that help the dough bake up flaky. And second: stretching the dough aggressively will make gluten production go into high gear, which results in stiff, tough pastry.
Before you roll it out, let your dough chill again for at least 30 minutes, preferably longer. That period of rest gives the gluten in the dough a chance to relax so that it's easier to roll out and won't shrink too much during baking.
It might be tempting to dust flour all over your countertop in preparation for rolling, but try to use some restraint: every spoonful that is worked into your dough will make it a little bit tougher. Use just enough to keep the dough from sticking and no more. Worried about mess? Try sandwiching the dough between sheets of parchment paper and rolling it that way.
Sweat the Details
Sometimes little things make all the difference. When you're making a double crust pie, don't forget to slice vents into the top—they'll help steam escape during baking and keep the bottom crust from turning soggy. And for a deep golden crust with nice shine, always brush the top of your pies with a wash of beaten egg with a splash of water or cream.
Turn Up The Heat
If you don't bake your pie at a high enough temperature, the crust will just stew in the fillings juices and never crisp up. (And no one wants that!) That's why most recipes recommend starting bakes at at least 425° F before reducing the temperature to 400°F or 375°F after about 30 minutes.
Offer A Shield
Sometimes pie fillings and crust cook at different paces. To make sure your crust doesn't scorch before the bake is finished, use a pie shield—or make one by placing a ring of aluminum foil over the edge of the crust during the last few minutes of baking.