Cupcakes:
Heat oven to 350° and line 24 cupcake tins with paper liners, lightly spraying them and setting them aside. In a small saucepan, melt the butter, vegetable oil and coffee, then set aside to cool slightly. Sift together the flour, cocoa, sugar, brown sugar, baking soda and salt. Slowly add the cooled coffee mixture to the dry ingredients and stir until combined. Add the eggs and whisk to combine, then mix in the buttermilk, applesauce and vanilla. Fill the prepared cupcake tins about three-fourths full. Bake for 20 to 22 minutes, or until the centers spring back when lightly touched or a toothpick inserted in the center comes out clean. Remove from the oven, transfer to a wire rack and allow the cupcakes to cool completely before frosting.

Frosting:
In a large bowl, beat the softened butter for 2 minutes until creamy. Slowly add the powdered sugar in four additions, beating until light and fluffy. Add the marshmallow topping and vanilla and mix until combined, then add the heavy cream. Frost the cooled cupcakes and top with cocoa nibs, miniature marshmallows or a drizzle of chocolate.