Grab your fork to dig into this rich, malty chocolate stout cake with Baileys buttercream, the perfect St. Patrick's Day dessert!
Preheat oven to 350 degrees F and grease two 8-inch round pans and line the bottoms with parchment rounds. Set aside.
Cut the butter into chunks and place in a small saucepan with the stout. Heat over med/low heat until butter is melted.
Whisk the cocoa powder into the stout/butter mixture. Set aside to cool.
Combine sugar and eggs in the bowl of a stand mixer or a large metal bowl. Beat until well mixed, about 2 minutes.
In a separate bowl, whisk together the dry ingredients.
Add the butter mixture to the sugar/eggs while beating on low. Mix until combined, about 2 minutes.
Add half of the dry ingredients, then half the buttermilk, the remaining dry, and ending with the remaining buttermilk. Stir in the vanilla.
Divide the batter evenly between the two prepared cake pans. Tap the pans on the counter once or twice to release some air bubbles. Bake, rotating the pans once during baking, for about 35 mins or until a toothpick inserted into the center comes out clean.
Cool the cakes for 5 mins on a wire rack in the pans, then remove from the pans to finish cool completely. Peel off the parchment. While the cakes are cooling, make the frosting.
Combine sugar and eggs whites in the bowl of a stand mixer or a large metal bowl.
Place over a pan of simmering water and cook, whisking frequently, until sugar is completely dissolved and isn't grainy when you rub it between two fingers.
Remove from the heat and using your electric mixer, beat on high with the whisk attachment until the meringue is thick and glossy and the bottom of the bowl no longer feels warm, about 7-8 minutes.
Add the butter, piece by piece, and mix until incorporated.
Switch to the paddle attachment and add the Baileys. Continue beating until light, smooth and completely homogenized. Add green food coloring (for St. Patrick's Day) if desired.
Once the cake is fully cooled, place one cake round on a cake plate or stand and spread about one third to one half of the buttercream frosting on top, spreading it to the edges.
Place the other round on top pressing down slightly. Fill in the sides of the cake with a little frosting. Use an offset spatula to spread the remaining icing over the top.
Smooth the top and sides, scraping off the excess frosting. Run the spatula under hot water, wipe the water off, and continue to smooth the cake.