Preheat oven to 350° F. Line two muffin tins with cupcake liners and set aside.

In a pot or large saucepan, simmer the beer and butter on medium until butter is completely melted. Add cocoa powder and chocolate chips and stir until your mixture is smooth. Take off heat and set aside to cool.

In a separate medium bowl, whisk together, sugar, flour, baking soda, baking powder, and salt. Set aside.

In mixing bowl, whisk eggs and sour cream together until smooth. Slowly add the cooled chocolate mixture. Next, add flour mixture and stir just until combined.

Scoop batter into prepared cupcake tin until cups are about ⅔ full. Bake for 15 to 18 minutes. Remove from oven when a toothpick inserted in the center comes out clean. Allow to cool on racks.

In a large saucepan, melt chocolate chips, cream, and butter on medium-low. Stir until smooth. Add your whiskey, stir, then remove from heat and set aside to let mixture cool/thicken.

While your ganache is cooling, scoop a hole into the center of each cooled cupcake with a cupcake corer or a large round frosting tip. Fill holes to the brim with thickened ganache.

In a bowl with an electric mixer, cream together butter, 4 tablespoons Bailey's, and confectioners' sugar. If consistency is too thick, add more Irish cream one tablespoon at a time until piping consistency is reached.

Spoon frosting into a pastry bag fitted with desired tip. I used a large star tip (Ateco 823 or Wilton 1M). Pipe it generously on top of each filled cupcake and enjoy!