Preheat the oven to 350 degrees. Line 2 muffin tins with fun green cupcake liners. Set aside.

In a large bowl combine the chocolate cake mix, sour cream, milk, oil, and vanilla. Mix well until combined. Add in the eggs one at a time and beat until mixed into the batter.

Fill the cupcake liners 2/3 of the way full.

Bake for 18-22 minutes or until a toothpick inserted in the center comes out clean.

Remove from the oven and cool completely on a wire rack.

To make the buttercream place the butter in a large bowl and mix with a mixer until smooth. Add in the powdered sugar 1/2 cup at a time until the frosting is smooth.

Beat in the peppermint extract and green food coloring and beat for 1 minute.

Add the milk, 1 tablespoon at a time until desired consistency is reached.

Pipe the green mint frosting onto the cupcakes. Top each cupcake with a chocolate mint.