1. Pulse flour, sugar, and salt in a food processor. Add butter and shortening, and process until mixture resembles coarse meal, about 10 seconds. Add water in a slow, steady stream just until dough holds together, no longer than 30 seconds (do not overprocess). Squeeze a small amount of dough; if it doesn't hold together, add more water.

2. Remove dough from processor, and knead once or twice. Divide in half; shape into disks. Wrap each in plastic; refrigerate until firm, 1 hour or overnight.