Buy a box of brownies (I use Duncan Hines). Bake the brownies as directed on the box. When the brownies are done, pull them out of the oven and cover them with miniature marshmallows. Put them back in the oven for 3 or 4 minutes (until the marshmallows are soft). While they are softening, make the frosting. Pull out the brownies and cover with the frosting.
Frosting: Melt 4 tablespoons of butter in saucepan (I do this while the brownies are cooking). Add 1/8 cup milk, 1/2 tsp vanilla, and 1 tablespoon cocoa. Bring to slow boil on medium heat. When boiling starts, remove from heat, mix in 2 cups powdered sugar until smooth. Pour immediately over marshmallows. Allow to cool completely before serving. I mean it. Don’t eat any until they are cool. Don’t say I didn’t warn you.
Oh, and these brownies are addictive. And they will make you fat as a pig, but very popular.