Preheat the oven to 350°F. Line a standard 12-cup cupcake pan with paper liners. Set aside.
Combine the hot chocolate mix with 1 cup boiling water and set aside to cool.
In a large mixing bowl, whisk together the flour, sugar, cocoa powder, baking soda, baking powder, and salt. Add the hot chocolate, vegetable oil, and vanilla. Mix until completely combined. Add the eggs and mix until just combined.
Fill each cupcake liner about 2⁄3 of the way and bake for 18- 20 minutes or until a toothpick can be inserted and come out clean. Place on a cooling rack to cool completely before frosting.
To make the marshmallow buttercream: in a large mixing bowl with a hand mixer or stand mixer with fitted paddle attachment, beat softened butter, marshmallow creme and vanilla until smooth and fluffy, about 2-3 minutes.
With the mixer on medium speed, slowly add the powdered sugar until completely combined. Transfer to a piping bag and frost each cupcake. Top with a sprinkle of cocoa powder and mini marshmallows.
Notes
Cupcakes will last in an airtight container for up to three days.
See my tips and tricks for making these Hot Chocolate Cupcakes above the recipe box.