The two secrets to light, flaky pastry dough are to use cold ingredients and to process it as little as possible. In a food processor, with your pulse button, it takes no time at all. Makes two piecrusts.

5 cups all-purpose flour
1/4 teaspoon salt
3/4 pound very cold unsalted butter,
    cut into very small pieces
3 egg yolks
4 tablespoons ice water

Put the flour and salt in the bowl of the food processor fitted with a metal blade. Pulse a few times to combine. Begin to add the butter, and pulse until the mixture starts to look like coarse meal (10 to 15 pulses). Add the egg yolks, then slowly pour in the ice water while processing (no more than 20 seconds). Pulse until dough just comes together - do not let it form a ball. If it holds together when you pinch it, it's ready. Place the dough in a plastic bag, form it into a flat round (like a round loaf of bread), and chill it for at least one hour before rolling it out.