You can use any frosting you like on a mug cake. I prefer to use frosting that can be made quickly. I suggest using:  - whipped cream (or coconut whipped cream) - chocolate chips + a dash of coconut oil or butter, melt it and stir - Peanut butter, almond butter, cashew butter, etc. - Peanut butter + chocolate chips, melt it and stir - Softened cream cheese + sweetener + vanilla, combine  - Sweetener + cinnamon, for a cinnamon sugar topping that tastes like a donut