Step 1

Preheat the oven to 350°F. Generously grease two 8-inch wide and 3-inch deep cake pans and line with parchment paper rounds.

Step 2

In a large mixing bowl, whisk together the flour, sugar, cocoa, baking soda, baking powder, and salt.

Step 3

In a medium bowl, whisk together the sour cream, vegetable oil, eggs, vanilla, and beer.

Step 4

Add the wet ingredients into the dry ingredients and stir with a spatula until just combined.

Step 5

Divide the batter between the prepared pans and bake for 35 to 40 minutes, or until a cake tester comes out clean. Cool the cakes in their pans for 30 minutes before carefully turning them out onto a cooling rack or wire rack to cool completely. If possible, freeze the cakes while you prepare the buttercream.

Step 6

In a large bowl, use an electric mixer or hand mixer to beat the butter until light and fluffy. Gradually add the powdered sugar then the Irish cream. Beat the mixture on high speed until very light, fluffy, and smooth, about 3 minutes. If the frosting is too thick, add a splash more Irish cream. If it’s too thin, add some more powdered sugar.

Step 7

Assemble:

Step 8

Place one cake layer a cake stand or serving plate. Frost the top of the cake generously, as this will become the filling. Use even more if you're decorating as a 'naked' cake as shown in the photos. Top with the other cake layer, flat side up.

Step 9

With an offset spatula, spread a very thin layer of frosting all over the cake. This layer is a crumb coat and should act like spackle. For the smoothest frosting, return the cake to the fridge or freezer until firm to the touch.

Step 10

Spread the remaining frosting all over the cake. If desired, focus the frosting on the top to maintain the 'naked' look. Refrigerate while you prepare chocolate drip.

Step 11

Place the chopped chocolate in a heatproof bowl. Bring the heavy cream to a simmer then immediately remove from heat and pour over chocolate. You can also do this in the microwave. Cover for a few minutes then stir until smooth.

Step 12

Allow to cool until it has thickened but is still pourable, about 10 minutes. Don’t place ganache in the fridge to cool. Test the consistency of the drip by pouring down the side of a glass. If it’s too thick, microwave for 5 to 10 seconds. If it’s too thin, allow to continue to cool.

Step 13

The cake can be stored, covered, at room temperature for up to 1 day or in the fridge for up to 3 days.