Produce the cake:

• The oven to 350 degrees Fahrenheit. Two 8-inch by 3-inch cake pans should be generously greased and lined with parchment paper circles.
• Mix the flour, sugar, cocoa, salt, baking soda, and baking powder in a sizable mixing dish.
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• Whisk the sour cream, vegetable oil, eggs, vanilla, and beer in a medium basin
• Add the wet components to the dry ingredients when just blended and stir with a spatula.
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• Bake the batter for 35 to 40 minutes, or until a cake tester comes out clean, after dividing it between the prepared pans. The cakes should cool for 30 minutes in their pans before being carefully flipped onto a wire rack to finish cooling. While you make the buttercream if at all possible, freeze the cakes.

Buttercream preparation:

• Use an electric or hand mixer to beat the butter in a big bowl until it’s light and fluffy. Add the powdered sugar and Irish cream one at a time. For about three minutes, beat the ingredients at high speed until it is incredibly smooth, light, and fluffy. Increase the amount of Irish cream in the frosting if it is too thick. Increase the amount of powdered sugar if it’s too thin.