Evenly spread cake batter onto lined baking sheet.
Bake for approximately 15 minutes or until a toothpick comes out clean when inserted in the center of the cake. Allow to cool completely.
Use a round cookie cutter (3 inches in diameter) to cut out 12 circles from your cake. (Extra cake can be used for cake pops or parfaits.)
Make your teal buttercream by beating 1 stick of butter, 2 cups powdered sugar and 2 tablespoons milk with an electric mixer. Once buttercream is smooth, add teal gel food coloring and mix until completely tinted.
Scoop teal buttercream into a decorating bag with a round piping tip, Wilton #10. Frost 6 of your mini cakes. Top with an unfrosted cake.
To make the green buttercream, beat ½ stick butter, 1 cup powdered sugar and 3 tablespoons milk. Add green gel food coloring.
Scoop green buttercream into a decorating bag with Wilton icing tip #233 attached.