In a large mixing bowl, combine flour, sugar and salt. Add butter and shortening. Combine by pinching with fingertips or pastry blender until fat evenly is distributed and broken into hazelnut-size pieces. (The mixture should hold together when pressed.)
Add water all at once, and stir a few times with a wooden spoon. Turn out onto plastic wrap, and loosely wrap. Gently knead into a ball and then divide in half. Covering each with plastic, press into 5-inch disks, and wrap well. Chill one hour to three days, or freeze for later use.