Preheat oven to 375°.
To prepare cookies, place first 3 ingredients in a large bowl; beat with a mixer at medium speed until well blended (about 5 minutes). Beat in 1 1/2 teaspoons vanilla. Add egg whites, 1 at a time, beating well after each addition.
Lightly spoon flour into dry measuring cups; level with a knife. Combine flour and next 4 ingredients (through 1/4 teaspoon salt), stirring well with a whisk. Add to butter mixture; beat well. Turn dough out onto a lightly floured surface (dough will be soft). Divide dough into 4 equal portions. Roll each portion to an 8-inch circle between 2 sheets of plastic wrap. Freeze dough 20 minutes or until plastic wrap can be easily removed.
Working with 1 portion of dough at a time (keep remaining dough in freezer), remove top sheet of plastic wrap. Cut dough with a 3-inch cookie cutter, dipping cutter in flour between each use; place cookies on baking sheets coated with cooking spray. Discard bottom sheet of plastic wrap; reserve remaining dough scraps. Repeat procedure with remaining frozen dough.
Gently gather reserved dough into a ball; repeat rolling, freezing, and cutting procedure.
Bake at 375° for 8 minutes or until cookies are lightly browned. Remove from baking sheet; cool on a wire rack.
To prepare vanilla icing, combine 1 cup powdered sugar and remaining ingredients in a small bowl; stir with a fork until combined. Drizzle icing over the cookies, or spoon into a small zip-top plastic bag; cut a tiny hole in 1 corner of bag, and pipe designs onto cookies.