1In a food processor pulse together flour, salt and sugar. Add butter and shortening. Pulse 8 to 10 times or until mixture resembles coarse crumbs and some of the butter is pea-size(alternately, combine in a bowl using a pastry blender or forks.)
Combine vinegar with cold water. While pulsing crumb mixture in processor, drizzle in just enough water mixture to form dough, 1/3 to 1/2 cup. (Dough will hold together when you pinch it.) Halve dough, wrap in plastic wrap and press into disks. Chill for 30 to 1 hour or until ready to use. May be frozen for up to 2 months. Makes 2 single crusts.