Stir together first 3 ingredients in a medium bowl; cut in butter with a pastry blender until crumbly. (Mixture will look very dry.) Gently press mixture together with hands, working until blended and smooth (about 2 to 3 minutes).
Shape dough into 2 (4-inch-long) logs. Wrap in plastic wrap, and place in an airtight container. Freeze up to 3 months.
Thaw dough overnight in refrigerator. Cut into 1/4-inch-thick slices, and place on a lightly greased baking sheet. Brush with milk.
Bake at 350° for 12 to 15 minutes or until lightly browned.
Note: Dough may be rolled into a 10- x 8- 1/4-inch rectangle on a lightly floured surface. Cut lengthwise into 8 strips and crosswise into 4 strips, using a pastry wheel or knife forming 32 squares. Place squares on a lightly greased baking sheet; brush with milk, and bake.