Lucky Little Whoopie pies

My dessert is called lucky little whoopie pies. I have never tried this dessert before but I hope it turns out well.

Ingredients

Cake:

- 1 box of Betty Crocker butter recipe chocolate cake mix

- 3 eggs

-1 cup of water

-¼  cup of vegetable oil

Frosting:

-¼ cup of vegetable shortening

-½  stick of butter

-⅛ cup of granulated sugar

-½ teaspoon pure mint extract

-1 tablespoon of milk

-2 cups of powdered sugar

-green food coloring

-1 cup lucky charms cereal marshmallows

This is my first time trying this dessert but i think it turned out pretty well and it tasted good.