The secret to homemade pastry dough is to avoid blitzing your butter to smithereens in the food processor. Leaving pea-size pieces of butter in the dough is key, because they will melt in the oven and release water, which will become steam. The steam helps to puff up the dough and contributes to that melt-in-your-mouth texture. The dough can be made up to 1 day ahead, covered, and refrigerated. Alternatively, it can be frozen for up to 1 month.
In a food processor, combine the flour, sugar, and salt and pulse to blend. Add the butter and pulse about 10 times, or until the butter is in pea-size pieces; do not overprocess. While pulsing the processor, add 1/3 cup of the ice water, then pulse just until moist clumps of dough form, adding more water 1 tablespoon at a time if necessary.
Transfer the dough to a work surface and divide it in half. If making a double crusted pie (such as an apple pie with a lattice), make one half slightly larger and shape each piece into a thick disk. If making a single crusted pie (such as a pecan pie), divide the dough in half and shape into disks (freeze the second disk for another use). Wrap individually in plastic wrap and refrigerate for at least 30 minutes before rolling out.