Preheat oven to 350 deg F.Follow the directions on the back of the box, except use the Guinness in place of the water.Tint the Vanilla Cream with a bit of green food coloring and place it into a baggie.Fill the cupcake liners 1/3 full, add the cream then cover with remaining cupcake batter.Reduce the heat to 325 to bake for 25 minutes.Cool before frosting.Beat the butter until creamy, add the sugar a little at a time until thick, add Bailey’s to combine. If more sugar is needed to thicken, add in gradually. This made enough to frost 6 cupcakes.I also just dusted some with powered sugar (the diet version).