What's better than one cookie? Two cookies stuffed with rich, creamy filling. Try one of these five flavors in our cookie sandwich recipe. [link: http://www.marthastewart.com/356829/chocolate-sandwich-cookies]
With an electric mixer on medium-high speed, beat butter until smooth. Add confectioners' sugar, and beat until light and fluffy. Stir in one of the flavorings. Use immediately.