Linzer Thumbprints
Prepare dough, bake, and let cool as directed. Once cool, place 2/3 cup powdered sugar in a large plastic bag. Add cookies, a few at a time, shaking to coat. Fill each with 1/2 teaspoon raspberry preserves. Top with toasted sliced almonds.
Almond-Cherry Thumbprints
Prepare dough as directed, except add 1/2 teaspoon almond extract with the egg yolks. Roll balls in 2 lightly beaten egg whites then in 1 cup finely chopped slivered almonds. Bake and let cool as directed. Fill each with 1 tsp. cherry pie filling, placing a cherry on top.
Triple Chocolate Thumbprints
Prepare dough as directed, except reduce flour to 1 1/4 cups and add 1/4 cup unsweetened cocoa powder with the flour. Roll balls in 2 lightly beaten egg whites then in 1 cup chocolate sprinkles. Bake as directed. Immediately press a chocolate Kiss into each.
Mint Sparklers
Prepare dough as directed, except add 1/2 teaspoon mint extract with the egg yolks. Do not grease cookie sheet. Roll balls in coarse red or green sugar. Bake as directed. Immediately place a red or green candy coating disk in the center of each cookie. Bake 1 minute more. If desired, use a toothpick to swirl melted disks slightly.
Peanut Butter and Jelly
Prepare dough as directed, except roll balls in 2 lightly beaten egg whites then in 1 cup finely chopped peanuts. Bake and let cool as directed. Fill with 1/2 teaspoon creamy peanut butter and 1/2 teaspoon grape jelly. Sprinkle with chopped peanuts.
Sprinkle Stars
Prepare dough as directed, except do not grease cookie sheet. Roll balls in assorted nonpareils. Bake and cool as directed. Spoon 3/4 cup canned or homemade vanilla frosting into a decorating bag fitted with a small star tip. Pipe frosting into each center.
Walnuts and Jam Thumbprints
Prepare dough as directed, except roll balls in two lightly beaten egg whites then in 1 cup finely chopped walnuts. Bake and let cool as directed. Fill each with 1/2 tsp. apricot or strawberry preserves.
Cookie Storage:
Layer filled Mint Sparklers and Triple Chocolate between waxed paper in an airtight container. Layer and store all others unfilled. Store at room temperature up to 3 days or freeze up to 3 months. To serve, thaw (if frozen) and fill as directed.