-
Preheat oven to 350 degrees Spray a 9-inch deep dish pie plate with baking spray. Set aside.
-
In a large bowl, using a hand-held mixer or stand mixer with a paddle attachment, beat butter until creamy. Add both sugars and beat until light and fluffy. Add egg and extracts, mixing well. Gradually add in cake mix and cornstarch, a little at a time, mixing until combined and dough has formed.
-
Fold in M&M's® White Peppermint and holiday sprinkles. Press dough into prepared pie plate.
-
Bake in preheated 350 degree F oven for 20-25 minutes or until the cookie cake is light golden brown and set in the center. Do not over bake. Allow cake to cool completely before decorating.
-
While cake is cooling, prepare buttercream frosting. In a large bowl, using a hand-held mixer or stand mixer with a paddle attachment, beat butter until creamy. Beat in peppermint extract. Slowly add the powdered sugar one cup at a time alternating with the milk, mixing until desired consistency is reached.
-
Fill piping bag with prepared frosting and pipe stars around border of cooled cookie cake. Top frosting with sprinkles and M&M's® Holiday Milk Chocolate or M&M's® White Peppermint.