01 -
Preheat the oven to 350°F. Grease and line two 8-inch cake pans with deep sides. Mix the flour, sugar, cocoa powder, baking soda, baking powder, and salt in a large bowl. Whisk together sour cream, oil, eggs, vanilla, and Guinness in another bowl. Combine wet and dry ingredients, stirring gently until just combined. Avoid overmixing.
02 -
Distribute batter evenly between the prepared pans. Bake for 35-40 minutes, or until a cake tester comes out clean. Allow cakes to cool in the pans for about 30 minutes before transferring them to a wire rack. For easier assembly, freeze the cakes before frosting.
03 -
Using a hand or stand mixer, beat softened butter until fluffy. Gradually add the sifted powdered sugar and Irish cream while mixing. Beat for about 3 minutes until the frosting is light and creamy. Adjust with extra Irish cream or powdered sugar for consistency if needed.
04 -
Position one cake layer on a serving plate. Spread a generous amount of buttercream on top as filling. Add the second cake layer, flat side up. Apply a thin 'crumb coat' layer of frosting around the cake and refrigerate until firm. Finish by frosting the entire cake with the remaining buttercream. Refrigerate.
05 -
Heat heavy cream until it simmers and pour it over the chopped chocolate. Cover for a few minutes, then stir until smooth and slightly cooled but still pourable. Adjust consistency if necessary.
06 -
Carefully pour the ganache over the top of the chilled cake, smoothing it out to the edges with an offset spatula. Create drips by carefully pouring ganache down the sides. Decorate with sprinkles or chocolate curls while the ganache is still unset. Refrigerate to firm up.