The amount of water you need to add to the flour can vary from four to six tablespoons -- on damp or humid days, less water is needed.
Place flour, salt, and sugar in the bowl of a food processor, and process for a few seconds to combine. Add butter, and process until the mixture resembles coarse meal, about 10 seconds.
With the machine running, add 5 tablespoons ice water in a slow, steady stream through the feed tube just until the dough holds together, 30 seconds.
Divide dough in half, and wrap each half in plastic wrap.