Preheat oven to 350°F and line a 12-cup muffin tin with paper liners or spray with non-stick spray.

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

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

Transfer the batter into the prepared muffin tins, dividing it equally among the 12 cups.

Bake for 20-24 minutes or until a tester comes out clean. Cool in the pan for 5 minutes before removing to cool on a wire rack. Cool completely before frosting.

Add the butter to the bowl of a stand mixer fitted with the paddle attachment and beat until smooth.

Add half of 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 extract, whipping cream, and food coloring (if using) 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. 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.