Perfect St. Patrick's Day Cake

Preheat the oven to 350 degrees F (175 degrees C). Line two 9-inch cake pans with parchment paper and lightly coat with cooking spray.

To make the cake: Pour stout into a saucepan and add butter; bring to a simmer over medium-low heat. Remove the pan from heat, then whisk in cocoa powder until smooth. Set aside to cool.

Beat eggs and sour cream in a medium bowl with an electric mixer until well combined. Stir in stout mixture until incorporated.

Mix flour, sugar, baking soda, and salt together in a large bowl. Pour stout mixture into flour mixture and gently combine with a spatula; pour batter into the prepared pans.

Bake in the preheated oven until a toothpick inserted into the center of a cake comes out clean, about 30 minutes. Let cakes cool in the pans for 5 minutes before inverting them onto wire racks to cool completely.

To make the frosting: Mix confectioners' sugar, butter, and Irish cream liqueur together in a medium bowl until smooth and spreadable. Add more sugar or liqueur to reach desired consistency. Spread 1/2 of the frosting on top of each cooled cake layer.

Place chopped chocolate into a heat-proof bowl. Bring cream to almost boiling in a small saucepan over medium-high heat; pour over chocolate. Add butter and stir until chocolate is melted and mixture is very smooth. Allow to cool until pourable but not thin or overly runny, 10 to 15 minutes.

Stack a cake gently on the other, frosting sides facing up. Carefully drizzle chocolate mixture over the top, allowing decorative drips to run down the sides.