Pinata Cupcakes

Preparation

1. Preheat oven to 350 degrees, and line cupcake liners in a muffin pan.
2. Make cupcake according to box directions or vanilla cupcake recipe or chocolate cupcake recipe.
3. Divide batter evenly between about cupcake liners.
4. Bake for 18-20 minutes. Let the cupcakes cool and then transfer to a wire rack.
5. While the cupcakes are baking, make the buttercream frosting. In a medium-sized bowl, combine the powdered sugar, butter, vanilla extract, and milk. Mix together with a spatula and then use an egg beater or mixer machine if you have one. This makes the frosting smoother and creamy.  Start with 3 cups of powdered sugar and if you need more, then add another ½ cup. If you want more frosting, you can double the amounts for the frosting recipe.
6. Once the cupcakes are cool, use a knife to cut a hole about 1 inch deep with a ¾ inch diameter. Remove the cupcake center, and slice off some of the bottom of the cupcake center. You will use this to cover your M&M filling and give you a level surface to add frosting to. Fill each cupcake with about a tbsp of mini M&M's. Place the top part of the cupcake center back on the cupcake. 
7. Frost the cupcakes, and top with sprinkles.
8. When you cut the cupcakes in half or take a bite of the cupcakes, the mini M&M's will come out. Surprise!