Combine the flour, sugar and salt in a large bowl. Using two knives, a pastry cutter or your fingers, cut the shortening into the dry mixture until it resembles a coarse meal.
Combine the milk and water in a measuring cup. While mixing with a fork, add the liquid, a little at a time, to the flour mixture. Keep adding liquid until the dough comes together and forms a ball. (You may not need to use all of the liquid.) Form the dough into two discs and wrap each in plastic wrap. Chill in the refrigerator for at least 1 hour. The dough can be made up to 2 days ahead and kept in the refrigerator.