Chill everything: Cut the butter into small cubes and chill it for at least 15 minutes. Keep your starter cold too. Cold ingredients help create flaky layers.

Mix the dry ingredients: In a large bowl, whisk 1 1/4 cups all-purpose flour with 1/2 teaspoon salt. For sweet pies, add 1 to 2 teaspoons sugar. For a double crust, double the entire recipe.

Cut in the butter: Add the chilled butter to the flour. Use a pastry cutter or your fingertips to work it in until the mixture has pea-sized pieces with some larger bits. Don’t overwork it.

Add starter: Stir in 1/2 cup cold sourdough starter or discard. The dough will start to clump but may still look dry in places—that’s okay.

Bring it together: Sprinkle in 1 to 3 tablespoons ice water, 1 tablespoon at a time, just until the dough holds when pressed. Add 1 teaspoon vinegar or lemon juice if you like. The dough should be shaggy, not sticky.

Form and chill: Turn the dough onto a lightly floured surface. Press it together and shape into a flat disk (two disks if doubling). Wrap tightly and chill for at least 1 hour, or up to 48 hours. Resting relaxes gluten and hydrates the flour.

Roll it out: Let the dough sit at room temperature for 5 to 10 minutes if it’s very firm. Roll into a 12-inch circle for a 9-inch pie pan, rotating and lightly flouring as you go to prevent sticking.

Fit the pan: Gently drape the dough into the pie plate without stretching. Trim overhang to about 1 inch, fold it under, and crimp. For a double crust, fill the pie, add the top crust, trim, crimp, and vent.

Chill again: Pop the prepared crust in the fridge for 20 to 30 minutes before baking. Cold dough holds shape and stays flaky.

Bake: For prebaking (blind baking), line with parchment, fill with pie weights, and bake at 400°F (200°C) for 15 minutes. Remove weights and bake 8 to 12 minutes more until lightly golden. For filled pies, follow your pie recipe’s baking instructions.