I love St. Patrick's Day -- it's like Christmas for the Irish! Now, I'm Irish-Italian, so I grew up celebrating both St. Patrick's Day, and St. Joseph's Day (which is on March 19th.) I don't mean to ignore one half of my heritage, but it's kind of hard to come up with a theme cupcake in honor of St. Joe. Hopefully he'll forgive me.
In honor of
their namesake, these cupcakes have Guinness dark chocolate cake with dark chocolate bits in the batter; Jameson whiskey-flavored whipped cream filling; and a simple Bailey's buttercream frosting.

If you don't already have a favorite dark chocolate cake recipe that can be adapted using Guinness, it's also super easy to create these using a dark chocolate cake box mix. Sift the cake mix into a bowl, and add one 11.2-oz bottle of Guinness, 1/2 cup vegetable oil, and 3 eggs. Stir in a 6-oz bar of dark chocolate that has been chopped into small bits, or alternatively, use 1 cup of dark chocolate baking chips. Bake according to the box directions.
When the cupcakes are cool, fill them with the whiskey cream mixture. The recipe is simple: whip up a cup of heavy cream, and add 2 tablespoons each of sugar and Jameson. Whip to combine.
The Baileys buttercream frosting is also simple. Beat 1 room temperature stick of unsalted butter, and gradually add 3 cups of powdered sugar along with however many tablespoons of Baileys (and possibly milk, if you don't want to go too heavy with the liqueur) until you get the taste and consistency that you want.
I am pretty sure these are my favorite cupcakes ever... and I say that as someone who doesn't even like chocolate cake all that much.