Follow the directions on the Betty Crocker Super Moist Cake Mix in White replacing the water with your beer of choice and adding green coloring to the mix. I used Sam Adams Beer.
Pour food coloring in slowly to achieve the desired color. Stay away from pastel and go more for St. Patrick's Day green.
Bake the Cake as normal making sure not to overcook or brown too much.
Let cake cool and put the cake into a food processor to break it up into fine pieces.
Take broken up cake out of food processor and place into a large mixing bowl.
Mix in a heaping tablespoon of white frosting. I used my hands, but I am sure you could use a spoon.
Put the cake into a beer mug and use your hands to push out as much air as you can. Fill it to the top.
Ice the top of the cake in the mug so it looks like foam.
If you want to get really festive, you can serve with Four Leaf Clover sprinkles on top.