Place the flour, salt, sugar and diced cold butter in a food processor. Process a few times, until the mixture looks like a coarse meal. Add the cold water and process again a few times. The dough should become more moist. Turn out of the food processor and gather into a ball. Lightly dust your countertop with flour, and knead the dough 3 to 4 times until it comes together. Shape into a flat ball, wrap in plastic wrap and refrigerate for until firm, about an hour.