My friends loved it. Then again, most of my friends are so wrapped up in law books they would love if someone made them a PBJ. The boy's family was the real test. Neither of his parents really drinks (for various reasons), so the novelty alone would not save the cake- it had to earn its praise.
1 cup (2 sticks) unsalted butter
3/4 cup unsweetened cocoa powder (preferably Dutch-process)
2 cups all purpose flour
2 cups sugar
1 1/2 teaspoons baking soda
3/4 teaspoon salt
2 large eggs
2/3 cup sour cream
Ganache Filling
2/3 cup heavy cream
2 tablespoons butter, room temperature
1 to 2 teaspoons Irish whiskey (optional)
Baileys Frosting (you will likely have extra)
5 to 7 cups confections sugar
2 sticks (1cup) unsalted butter, at room temperatue
8 tablespoons Baileys (or milk, or heavy cream, or a combination thereof)
Instructions
Whisk flour, sugar, baking soda, and 3/4 teaspoon salt in large bowl to blend. Using electric mixer, beat eggs and sour cream in another large bowl to blend. Add stout-chocolate mixture to egg mixture and beat just to combine. Add flour mixture and beat briefly on slow speed. Using rubber spatula, fold batter until completely combined. Divide batter among pans. Bake cake until tester inserted into center comes out clean, about 25-35 minutes. Cool slightly in pans, then remove to rack to cool completely.
Make the filling: Place chocolate chips in a heatproof bowl. Heat the cream until simmering and pour it over the chocolate. Let it sit for one minute and then stir until smooth. (If this has not sufficiently melted the chocolate, you can return it to a double-boiler to gently melt what remains. 20 seconds in the microwave, watching carefully, will also work.) Add the butter and whiskey (if you’re using it) and stir until combined.
Let the ganache cool until thick but still soft enough to be piped (the fridge will speed this along but you must stir it every 10 minutes). At this point you can either spread the ganach directly onto the top of your bottom layer of cake, or, what I like to do is use a mixer to beat slightly to aerate it and make it more of a frosting consistency. If it doesn't fluff like a frosting, it is not cool enough yet and will slide off the cake. Spread on the cake as the filling between the layers.
Make the frosting: Whip the butter in the bowl of an electric mixer, or with a hand mixer, for several minutes. You want to get it very light and fluffy. Slowly add the powdered sugar, a few tablespoons at a time. When the frosting looks thick enough to spread, drizzle in the Baileys (or milk) and whip it until combined. If this has made the frosting too thin (it shouldn’t, but just in case) beat in another spoonful or two of powdered sugar.
Assemble the cakes into layers and then frost. You can also use any leftover ganache to decorate the top by piping it on with a bag.

