Preheat oven to 350 degrees. Mix ingredients until combined (batter will be thick). Drop spoonfuls of batter onto the baking sheet about two inches apart. Bake 10-12 minutes and allow to cool. Once cooled, fill with buttercream frosting by spooning a small amount of frosting on the flat side of one cookie. Take another cookie and press together until frosting us spread evenly between both sides and visible from the sides.