For the Cake:

1. Preheat the oven to 300°F and liberally butter two 9-inch round pans (See important NOTE below).
2. Place the butter and chocolate chips in a small bowl and place in the microwave for 30 seconds. Stir and then microwave again for another 15 seconds. Stir until the butter and chocolate are both melted and glossy.
3. Into a large bowl, whisk together sugar, flour, cocoa powder, baking soda, baking powder, salt, and espresso powder.
4. In the bowl of a stand mixer, beat the eggs until lightened in color and slightly frothy, about 2 minutes.
5. Stir in the cooled butter and chocolate mixture.
6. In a large measuring cup, stir together the oil, stout beer, buttermilk, and vanilla (don’t be alarmed if it looks a little curdled before it gets mixed into the other ingredients).
7. Slowly add the buttermilk mixture to the egg mixture, mixing until well combined.
8. Add the dry ingredients to the wet mixture in two or three batches, mixing until just combined. Resist the urge to overmix the batter. You want to mix until all the dry ingredients are visibly incorporated.
9. Place the cake pans on a large baking sheet. Divide the batter between the prepared pans and bake in the middle of the oven until a tester inserted in the centers comes out clean, roughly 60-75 minutes (check after an hour).
10. Cool the cakes in the pans for 15 minutes and then carefully invert them onto cooling racks to finish cooling.
11. Cake layers may be made a day or two ahead and kept, wrapped well in plastic wrap, in the fridge. I actually prefer to do the cakes ahead because they are easier to frost if chilled.

For the Whiskey Fudge Filling:

1. In a saucepan, bring cream, sugar, and salt to a simmer over moderately low heat, whisking until sugar is dissolved.
2. Remove pan from heat and add chocolate, whisking until chocolate is melted. Stir in the whiskey.
3. Cut butter into pieces and add, whisking until smooth. Whisk in the powdered sugar until smooth.
4. Transfer the mixture to a bowl and cool, stirring occasionally, until spreadable. This should take 20-30 minutes. You want it to be of a fudgy consistency so that it does not run out the sides of the cake during assembly. I let it cool until it is a similar consistency to frosting.

For the Bailey’s Buttercream: 

1. In the bowl of a stand mixer, cream together the cream cheese and butter with the whisk attachment for 2 minutes, or until they are fluffy, creamy, and well combined.
2. Add in the salt, Bailey’s and vanilla and whisk on low speed to combine.
3. Add in half of the powdered sugar and mix until combined. Add the remaining powdered sugar and beat the frosting until it is thick and creamy.

To Assemble:

1. Place the first cake layer on a cake pedestal (or plate). Spread the cooled fudge filling mixture on top of the first layer. Do not go all the way to the edge. Top with the second cake layer.
2. Dollop half of the frosting on top of the cake and work it around the top and down the sides, swirling the frosting evenly as you go. This will serve as a “crumb coat.” Place the cake in the fridge for 20-30 minutes so the first layer of frosting can set.
3. Spread the second layer of frosting over top of the first (this will cover up any cake crumbs that have worked their way into the first layer of frosting), smoothing everything out as you go.
4. Slice and serve! Store any leftover cake well wrapped in the fridge and allow enough time to let it come back to room temperature before serving again (See NOTE below).