Directions

1. In the bowl of a stand mixer, combine the cake mix, the butter, water, and the eggs until thoroughly combined.
2. Set aside half of the batter. Add red food coloring to the batter in the stand mixer, and add blue food coloring to the batter you've set aside. Mix until it reaches your desired color, adding more food coloring if necessary.
3. Place the two batters in separate piping bags. Pipe the cookies onto a parchment-lined baking sheet; make them approximately 1 ½ in diameter.
4. Bake in a 375-degree oven for about 10 minutes or until the tops of the cookies spring back when touched. Remove from the oven and allow to cool completely.
5. To create the filling: place the butter, vanilla, powdered sugar, and milk in the bowl of a stand mixer and beat until thick and smooth.
6. Once the cookies are completely cool, pipe the red cookies with filling and top with the blue cookies.