Combine flour, baking powder, and salt; cut in butter and shortening with pastry blender until mixture resembles coarse meal. Sprinkle milk evenly over surface; stir with a fork until dry ingredients are moistened. Shape into a ball; chill. Roll dough to 1/8-inch thickness on a lightly floured surface. Fit pastry into an 11x 7-1/2x 1-inch tart pan or into six (4-inch) tart pans. For baked tart shells, prick bottom of pastry generously with a fork. Bake at 450 degrees for 12 to 15 minutes or until lightly browned. (4-inch) tarts. NOTE: The butter in Tart Pastry gives this recipe extra strength to stand up on its own, since tarts are served out of the pans in which they were baked. You can bake this pastry in one large tart pan, or six small ones. Look for these shallow pans with removable sides in kitchen specialty shops. They may be called tart or quiche pans. ----