In a large mixing bowl combine the cake mix, water, oil, eggs, vanilla, and coffee liqueur mixture. Using a hand mixer, mix on low until combined for about 30 seconds, then increase to medium speed and beat for 2 minutes. Scoop the batter evenly into the lined cupcake pan. Bake for 18-20 minutes or until toothpick comes out clean. Remove from pans onto a cooling rack, cool completely before frosting.
Additional topping idea: chocolate covered coffee beans!
For a more dense cake texture add an additional egg.