Preheat oven to 190C/350F/Gas5 and place cupcake liners in a cupcake pan.

Sift together the flour, cocoa powder, baking powder, baking soda, and salt in a small bowl. Set aside.

Place the butter, sugar, and eggs in a large bowl and whisk together. Add the sour cream and whisk to combine.

Slowly whisk dry ingredients into the bowl of wet ingredients, one third at a time. When combined, add the hot coffee and stir.

Use an ice cream scoop to fill each cupcake liner with batter. This mix makes 12-16 cupcakes.

Bake for 15-17 minutes or until a toothpick comes out clean when inserting into the center of one cupcake.

Transfer to a wire rack to cool completely.

Once cupcakes are cool, use a cupcake corer or a knife to carve out a hole in the center of each cupcake, about ¾" diameter and ½" deep.

Fill each cupcake hole with marshmallow fluff.

To make the buttercream use an electric mixer to beat together the butter, powdered sugar, marshmallow fluff, and milk on low to start, increasing the speed until ingredients are combined, smooth, and form semi-stiff peaks.

Scoop the buttercream into a piping bag with Wilton icing tip #12 attached and pipe a ghost on top of each cupcake.

To make the face of one ghost, roll out 2 small balls from the black fondant - about ¼" and flatten them out to make the ghosts' eyes. Then roll a more oval shape and flatten to form the mouth. Place onto the frosting ghosts and serve!