Brownie cupcakes with marshmallow frosting are kind of like a s’more minus the graham cracker holding the whole thing together. The only difference, except for the s’more, is the thick brownie texture of the cupcake, which takes the place of the Hershey chocolate bits quite nicely. The marshmallow frosting? It is made from vanilla extract, cream of tartar, granulated sugar and egg whites. After frosting the cupcakes, apply a liberal helping of the frosting before toasting it lightly. The results are pretty close to the real thing, only tastier!
Source Cooking Classy