Spread on large (10x15x1 inch) greased cookie sheet. Bake 25 minutes at 350. Remove from oven and cover entire top with 1 package of miniature marshmallows. Return to oven for 3 minutes, until soft and puffy. Cool and frost with chocolate frosting.Chocolate Frosting:
1/4 cup milk
1-2 tsp vanilla (depending on your taste)
3 tablespoons of cocoa
2-3 cups of powdered sugar
Mix all ingredients with a hand mixer until smooth. Add more powdered sugar or milk until you reach desired consistency and spread on top of bars.