If using a food processor: To the jug of a food processor, add flour, baking powder, salt, sugar, and cold butter. Pulse a few times until the mixture is crumbly and resembles coarse sand. Do not over-mix.
Using your hands flatten the dough into a ¾ inch-thick rectangluar disk, then fold one side to the center, and then the other side to the center, and fold the whole thing over again. Repeat two times and you should end up with a ¾-inch thick rectangle.