To make the cupcakes, start by preheating your oven to 350 degrees. Spray a muffin tin or add cupcake liners.
In a large bowl, mix together cocoa, baking soda, baking powder, hot chocolate mix, cake flour, sugar, milk, eggs, and oil. Mix with a mixer 2-3 minutes, until smooth.
Pour mixture into a cupcake liners or muffin tin, 2/3 full.
Bake 20-22 minutes.
To make the frosting, cream together the butter, marshmallow fluff, vanilla, and salt.
Alternate adding small amounts of the powdered sugar and heavy cream, mixing between each addition.
If your icing is too runny, add more powdered sugar until the desired consistency is reached.
Allow the cupcakes to cool completely before frosting. Add a small layer of frosting, then top with mini marshmallows and a fun paper straw. Enjoy!