For the Guinness chocolate cupcakes:
1 cup stout (Guinness)
16 tbsp. unsalted butter
¾ cup unsweetened cocoa powder
2 cups all-purpose flour
2 cups sugar
1½ tsp. baking soda
¾ tsp. salt
2 large eggs
2/3 cup sour cream
For the Bailey’s ganache filling:
8 oz. bittersweet chocolate, finely chopped
2/3 cup heavy cream
2 tbsp. butter, at room temperature
2 tsp. Bailey’s Irish cream (or Jameson whiskey)
For the Bailey’s buttercream frosting:
8 tbsp. unsalted butter, at room temperature
3-4 cups confectioners’ sugar, sifted
4-8 tbsp. Bailey’s Irish cream
To make the cupcakes, preheat the oven to 350° F. Line two cupcake pans with paper liners. Combine the stout and butter in a medium saucepan over medium heat. Add the cocoa powder and whisk until smooth. Remove from the heat and allow to cool slightly.
In a large mixing bowl, combine the flour, sugar, baking soda and salt. In the bowl of an electric mixer fitted with the paddle attachment, beat together the eggs and sour cream to blend. Add the stout-butter mixture and beat just to combine. Mix in the dry ingredients on low speed just until incorporated. Divide the batter evenly between the cupcake liners, filling them about 2/3 to ¾ full. Bake until a toothpick inserted in the center comes out clean, about 17 minutes. Allow to cool in the pan for 5-10 minutes, then transfer to a wire rack to cool completely.
To make the ganache filling, place the chocolate in a heatproof bowl. Heat the cream in a small saucepan until simmering, then pour it over the chocolate. Let sit for one minute and then whisk until smooth. If the chocolate is not completely melted, place the bowl over a double boiler or give it a very short burst in the microwave (15-20 seconds). Add the butter and Bailey’s and stir until combined.
Set aside to let the ganache cool until it is thick enough to be piped. (You can use the refrigerator to speed the cooling process, but be sure to stir every 10 minutes or so to ensure even cooling.) Meanwhile, cut out a portion from the center of the cupcake using the cone method (a small paring knife works best for this). Once the ganache has reached the correct consistency, transfer it to a piping bag fitted with a wide tip and pipe it into the cupcakes.
To make the frosting, place the butter in the bowl of a stand mixer fitted with the paddle attachment. Beat on medium-high speed until light and fluffy, about 2-3 minutes. Gradually add the powdered sugar until it is all incorporated. Mix in the Bailey’s until smooth. Add more if necessary until the frosting has reached a good consistency for piping or spreading. Frost the cupcakes as desired.