For the cake:
- 1 cup Guinness stout
- 1 1/2 sticks (12 tablespoons) unsalted butter
- 2 ounces semisweet chocolate, chopped
- 3/4 cup dark cocoa powder, divided
- 1/2 cup malted milk powder
- 1 3/4 cup granulated sugar
- 3/4 cup sour cream
- 2 large eggs
- 1 1/3 cups all-purpose flour
- 2 tablespoons cornstarch
- 1/2 tablespoons baking soda
- 1/2 teaspoon salt
For the frosting:
- 2 sticks (16 tablespoons) unsalted butter, softened at room temperature
- 2 cups powdered sugar, plus more, if needed
- 1/4 cup Baileys Irish Cream liqueur
- 1/2 teaspoon salt
For the chocolate curls:
- 3 ounces semisweet chocolate
- 1 tablespoon vegetable shortening
- Preheat the oven to 350 degrees F. Grease a 1.5 lb loaf pan and sprinkle with 1/4 cup cocoa powder. Shake the cocoa powder around to coat.
- In a large pot over medium heat, combine the stout, 1 1/2 sticks of butter, and 2 ounces of semisweet chocolate. Heat until melted and smooth, stirring occasionally.
- Remove the pot from the heat and stir in the remaining 1/2 cup cocoa powder and the malted milk powder. Once well-combined, stir in the sugar. Let cool for 10 minutes.
- Stir in the sour cream and eggs once the chocolate mixture has cooled. Set aside.
- In a large bowl, whisk together the flour, cornstarch, baking soda, and 1/2 teaspoon salt. Add the dry mixture to the chocolate mixture and stir until just combined.
- Pour the cake batter into the loaf pan and smooth with a rubber spatula or the back of a spoon. Bake for 45 minutes, or until a toothpick inserted into the center of the cake comes out clean. Once finished baking, let sit in the pan for 15 minutes to cool, then gently remove from the pan and transfer to a wire rack to finish cooling.
- While the cake bakes and cools, make the frosting. In a stand mixer or a large bowl using a hand mixer, beat the 2 sticks of butter until fluffy. Add in the powdered sugar, a bit at a time, and mix until thick and well-combined. Slowly stream in the Baileys as you mix, until smooth, and finally add in the salt. If the mixture is too thin, add a tablespoon of powdered sugar at a time until the frosting reaches the desired thickness. Set aside.
- To make the chocolate curls, combine the remaining semisweet chocolate and vegetable shortening in a microwave safe bowl and heat in 15-second intervals, stirring between, until completely melted and smooth. Pour the melted chocolate mixture onto the back of a metal baking sheet and smooth into a thin, even layer using a rubber spatula or knife. Place the baking sheet in the freezer to cool for 2 minutes.
- Remove the baking sheet from the freezer, and using a sharp-edges spatula, scrape the chocolate from the bottom of the pan. As you press forward, the chocolate will curl. If the chocolate gets too soft, transfer it back to the freezer for a minute, making sure not to let the chocolate get too frozen or it will break apart.
- Frost the cake and place the chocolate curls on top. Serve.