Preheat oven to 350F. Line a cookie sheet with parchment or a silpat and set aside.
In a medium-sized bowl, combine the flour, baking powder and spices- set aside.
Cream together the butter and sugars until light and fluffy. Add the egg yolks, eggnog and vanilla and beat until smooth and creamy.
Gradually add in the dry ingredients until well-combined (don't over-mix.)
Use a cookie scoop or tablespoon to portion off 1 1/2 inch sized dollops of dough and roll into a ball shape before placing on the cookie sheet 2 inches apart.
Bake for 12-14 minutes, or until the edges seem set and just slightly golden. Cool completely before frosting.
For Frosting:
Cream the butter until light and fluffy. Add in the 3 cups of powdered sugar gradually, until mixture is dry and crumbly. Add the egg nog, spices and extract if using. If you want a very stiff frosting that will dry hard, add more powdered sugar if needed. If you want a smoother frosting add a little more egg nog until you reach your desired consistency.
Recipe adapted from: All Recipes