Step 1

Preheat the oven to 350°F. Line a 12-cup muffin tin with cupcake liners.

Step 2

In a large mixing bowl, whisk the flour, sugar, cocoa powder, baking soda, and salt until evenly combined.

Step 3

In a medium bowl, whisk together the egg, milk, vegetable oil, and vanilla extract.

Step 4

Gradually add the wet ingredients to the dry ingredients, mixing until just combined. Stir in the hot coffee (or hot water) until the batter is smooth and well blended.

Step 5

Divide the batter evenly among the cupcake liners, filling each about two-thirds full. Bake for 18-20 minutes or until a toothpick inserted into the center comes out clean. Let the cupcakes cool in the tin for 5 minutes before transferring them to a wire rack to cool completely.

Step 6

In a medium bowl, beat the softened butter with an electric mixer until creamy. Gradually add the powdered sugar, beating until light and fluffy. Fold in the marshmallow creme and vanilla extract until fully combined. Transfer the filling to a piping bag fitted with a small round tip.

Step 7

Place the chocolate chips in a heatproof bowl. Heat the cream in a small saucepan over medium heat until it just begins to simmer. Pour the hot cream over the chocolate and let it sit for 2 minutes. Stir until the mixture is smooth and glossy. Let the ganache cool slightly before using.

Step 8

Use a small knife to cut a cone-shaped piece from the center of each cooled cupcake (keep the cut-out pieces for snacking or discard them). Pipe the marshmallow filling into the cavity of each cupcake, filling just to the top.

Step 9

Dip the tops of the filled cupcakes into the chocolate ganache, ensuring an even coat. Place the cupcakes on a wire rack and let the ganache set at room temperature.

Step 10

In a small bowl, whisk together the powdered sugar, milk, and vanilla extract until smooth and thick. Transfer the icing to a piping bag fitted with a small round tip.

Step 11

Pipe the signature curly line design onto the top of each cupcake once the ganache has fully set. Let the icing firm up slightly before serving.