Preheat the oven to 350 degrees. Line a cupcake pan with cupcake liners and set aside.
Place the marshmallows into a saucepan over medium heat until melted, stirring constantly. Set aside.
In a bowl cream the butter, incorporate the sugar and beat until light and fluffy (around 3 minutes).
Incorporate the melted marshmallows.
Incorporate the eggs one at a time, mixing well after each addition.
Add the baking powder and the vanilla.
Incorporate the milk and the flour alternating between the two of them, starting and finishing with the flour.
Mix until everything is well incorporated and there are no lumps left (the batter should be shiny)
Divide the batter between the cupcake liners in a 12-Cup Regular Muffin Pan and take to the oven.
Bake for 17 minutes or until done. Remove from the oven and from the cupcake pan and let them cool down until they are no longer hot to the touch.
Meanwhile, whip up the hot chocolate frosting. In the bowl of a mixer add the butter and sugar and whisk until light and fluffy (around 4 minutes).
Incorporate the cocoa powder, vanilla, cinnamon, and nutmeg mixing well after each addition. Slowly pour the melted chocolate and whisk until well incorporated.
Fill a piping bag with the frosting. I love the Wilton 12-Piece Cupcake Decorating Set, and it's under $7.00.
Decorate each cupcake with the frosting, serve and enjoy.