Combine flour, sugar and salt in large bowl. Add butter and shortening. Cut in using hands or pastry blender until mixture resembles coarse meal. Add buttermilk and stir with fork until moist clumps form. (Dough can also be prepared in processor. Using on/off turns, cut butter and shortening into dry ingredients until coarse meal forms. Add buttermilk and process just until moist clumps form.) Press together to form dough. Divide dough in half. Gather dough into balls; flatten into disks. Wrap separately and chill 1 hour. (Can be prepared ahead. Refrigerate 1 week or freeze 1 month. Let dough stand at room temperature to soften slightly before using.)
