1. Sift sugar and cocoa powder together into a large mixing bowl.
2. Place the marshmallow creme, butter, and milk in heavy saucepan over medium-low heat.
3. Stir until melted, 2-3 minutes and remove from heat.
4. Pour the sugar-cocoa mixture over the marshmallow mixture and add the vanilla.
5. Stir until the frosting is smooth and satiny.