Preheat the oven to 350°F and line a cupcake pan with 4 paper liners.
In a mixing bowl, whisk together the flour, granulated sugar, black cocoa powder, 1 teaspoon espresso powder, baking soda, and salt.
Add the milk, vegetable oil, egg, and vanilla extract to the dry ingredients. Stir until the batter is smooth and no lumps remain.
Divide the batter evenly among the 4 liners. Bake for 18 minutes or until a toothpick inserted in the center comes out clean. Cool the cupcakes completely on a wire rack.
In a clean bowl, beat the softened butter with an electric mixer until creamy. Gradually add the powdered sugar and remaining 1 teaspoon espresso powder, then mix in enough black food coloring to reach a deep black shade. Add a splash of milk if the frosting feels too thick.
Spread or pipe the black frosting over each cooled cupcake. Press two chocolate chips into the top of each for ears and add short licorice pieces below for whiskers.