To make the frosting, add butter to a large stand mixing bowl and mix on high speed for 1 minute.
Turn speed to low and slowly add powdered sugar until mostly incorporated.
Pause to scrape the sides of the bowl, add marshmallow fluff and heavy cream.
Continue to mix on high speed for 1 - 2 minutes until a light and fluffy consistency has been achieved. Transfer frosting to a piping bag and set aside.
Decorating the Snowmen Cupcakes
To decorate the cupcakes, use a black edible marker to draw eyes and mouth. Use orange food gel to create the nose.
To make a snowman hat, roll out the black fondant to a thin layer. Using the round end of a piping tip cut out small circles for the base. In your hand, roll a small amount into a ball and slightly press down to create the top of the hat.
When cupcakes have completely cooled, add frosting, marshmallow and hat, in that order.