Preheat the oven to 350°F and line a 12-cup muffin tin with paper liners or spray with gluten-free nonstick spray.

In a medium bowl, whisk together the flour, xanthan gum, cocoa powder, baking soda, salt, and sugar. Set aside.

In a large bowl, whisk together the egg, milk, oil, and vanilla. Add dry ingredients to the wet ingredients and stir until just combined. Stir in the hot coffee until completely incorporated.

Divide the batter evenly into the prepared muffin tins. Bake for 20-24 minutes or until a tester comes out clean. Cool in the pan for 5 minutes before transferring to a wire rack. Cool completely before frosting.

Add butter to the bowl of a stand mixer fitted with the paddle attachment and beat until smooth. Add half the powdered sugar and a pinch of sea salt and beat on low until the sugar is mostly incorporated. Add the remaining powdered sugar and beat on low until combined. Increase speed to medium and beat for 3 minutes.

Stop the mixer and scrape down the bowl. Add the vanilla and cream and beat for an additional minute on low, increasing the speed to medium once the whipping cream is incorporated.

Transfer the frosting to a piping bag fitted with a large round piping tip (I used an Ateco 809 piping tip but a Wilton 1A would also work well). Pipe a tall swirl on top of each cupcake to form the ghost.

Place two mini chocolate chips on each cupcake for the eyes with the point of the chocolate chip facing in.

Store in an air-tight container and serve at room temperature. Can be frozen.