Directions for Cupcakes:

1. Preheat the oven to 350 degrees Fahrenheit.
2. Line a 12-serving cupcake pan with paper cupcake liners. Set aside.
3. Add the flour, cocoa powder, baking powder, baking soda, and sugar to a small mixing bowl and whisk to combine.
4. Add the melted butter, vanilla, hot cocoa, coffee, and egg to a large mixing bowl and beat with an electric mixer until smooth and creamy.
5. Carefully spoon or pour the batter into the prepared cupcake pan until each liner is about ¾ full.
6. Bake for 18 minutes, or until a toothpick inserted into the center of one of the cupcakes comes out with only moist crumbs on it.
7. Remove the cupcakes from the pan and place them on a wire cooling rack to cool completely.

Directions for Buttercream:

1. Add the butter, vanilla extract, powdered sugar, and milk to a large mixing bowl and beat with an electric mixer until creamy, scraping down the sides of the bowl periodically with a rubber spatula to ensure all ingredients are fully incorporated.
2. Spoon the frosting into a large decorating bag that is fitted with a large star tip.
3. Swirl the frosting onto each cupcake.
4. Add the ½ cup chocolate chips to a small microwave-safe bowl and microwave in 30-second intervals until fully melted, stirring the chocolate after each interval.
5. Pour the melted chocolate into a small ziplock bag and snip a very small corner off the bag.
6. Drizzle the chocolate over the cupcakes.
7. Top each cupcake with chocolate chips and small marshmallows.
8. Store any leftover cupcakes in an airtight container for up to three days.