Place the cubed butter in the freezer for 10–15 minutes. If possible, chill your mixing bowl as well. Keeping everything cold is key for a flaky, all-butter crust.

In a medium bowl, whisk together the flour, salt, and sugar (if using) until evenly combined.

Add the cold butter cubes to the flour mixture. Using a pastry cutter, two knives, or your fingertips, cut the butter into the flour until you have pea-sized pieces with some slightly larger, flat bits. Visible pieces of butter are desirable for flakiness.

Stir in the vinegar or lemon juice. Drizzle in about 3 tablespoons of ice water, tossing gently with a fork. If the dough is still dry and floury, add more ice water 1 tablespoon at a time until the dough starts to clump when squeezed. It should hold together but not feel sticky or wet.

Turn the shaggy dough out onto a lightly floured surface. Gently press and gather it into a rough disk. Use a gentle press-and-fold motion once or twice to help it come together. Do not knead like bread; avoid overworking to keep the crust tender.

Shape the dough into a 1-inch-thick disk. Wrap tightly in plastic wrap or reusable wrap and refrigerate for at least 1 hour and up to 3 days to allow the flour to hydrate and the gluten to relax.

Lightly flour your work surface and rolling pin. Unwrap the chilled dough and let it sit at room temperature for about 5 minutes if very firm. Roll from the center outward, rotating the dough a quarter turn every few rolls, until it is about 12 inches in diameter and roughly 1/8 inch thick. If edges crack, pinch and press them back together.

Carefully roll the dough around your rolling pin and unroll it over a 9-inch pie dish. Gently ease the dough into the bottom and sides of the dish without stretching it. Let the excess hang over the rim.

Using kitchen scissors or a small knife, trim the overhang so you have about 1/2–1 inch beyond the rim. Fold the excess under itself to create a thicker edge, then crimp with your fingers or press with a fork. Chill the shaped crust in the refrigerator for 20–30 minutes before baking to help it hold its shape.

For pies with liquid or custard fillings, preheat the oven to 400°F (200°C). Line the chilled crust with parchment paper or foil and fill with pie weights, dry beans, or rice. Bake for about 15 minutes, then carefully remove the weights and lining. Bake 8–12 minutes more for a partially baked crust, or until fully golden for a fully baked crust.

For a glossy, golden finish on a top crust or on the edges of a single crust, beat together the egg, milk or cream, and a pinch of salt. Brush lightly over the crust just before baking.