Here is a recipe for homemade marshmallow icing from an Amish Cookbook that I use all the time. I pipe in into cupcakes, so yum 

1 cup sugar
1/4 cup water
Pinch of salt
1 egg white
1 teaspoon vanilla extract

Mix sugar, water and salt together in a small sauce pan over a low heat, stirring until sugar is disolved. Beat egg white until stiff peaks are formed. Continue beating the egg while pouring the hot syrup into it in a steady thin stream. After all the syrup is added continue beating until very thick and rounded peaks form.

This tastes exactly like the inside of a chocolate snowball! You could also add 2 tablespoons of chocolate to the warm icing to make choc icing, or to colour it add strawberry, raspberry or cranberry juice for a pink shade.