Prepare the cupcakes according to the package directions. Bake and allow to completely cool.

Meanwhile, empty both cans of frosting into a bowl. Add a few drops of green food coloring and mix until you reach the desired color. Set aside.

Cut the mini marshmallows in half. Set aside.

Place the powdered sugar in another bowl and add the water, 1 tablespoon at a time, until a thick icing forms. Add a few drops of black food coloring, mix, and set aside.

Put the green frosting into a piping bag and pipe on to all 24 cupcakes.

Place the marshmallows, cut side down, on the cupcakes in groups of 1, 2, or 3.

Put the black icing into a piping bag with a small tip and pipe a black dot in the center of each marshmallow to create the eyes. Then pipe on a straight line, squiggly line, or a round circle for the mouth.

Cut the spearmint leaves into 4 pieces for the ears. Place one on each side of the cupcake. If desired place one on the top of the cupcake as well.

Allow the cupcakes to sit for about an hour before placing them in a cupcake container or a bakery box.