This recipe reimagines the classic whiskey-spiked Irish coffee as a decadent mocha layer cake filled with coffee-whiskey whipped cream and topped with white and dark chocolate shavings.
For the cake layers
Unsalted butter for the pans
10-1/8 oz. (2-1/4 cups) unbleached all-purpose flour
2 cups granulated sugar
2-5/8 oz. (3/4 cup) unsweetened natural cocoa powder
1-1/2 tsp. baking powder
1-1/2 tsp. baking soda
1 tsp. table salt
2 large eggs
1 cup whole milk
1/2 cup canola oil
1-1/2 tsp. pure vanilla extract
1 cup hot coffee
For the coffee-whiskey whipped cream
1 Tbs. instant espresso granules
1/4 cup Irish whiskey, such as Jameson
3 cups heavy cream
3 Tbs. packed dark brown sugar
To finish the cake
1 4-oz. block semisweet chocolate (about 1-inch thick), at room temperature
1 4-oz. block white chocolate (about 1-inch thick), at room temperature
Make the cake
Position racks in the upper and lower thirds of the oven and heat the oven to 350°F. Butter three 9x2-inch round cake pans and line the bottoms with parchment. Butter the parchment.
In a stand mixer fitted with the whisk attachment (or in a large bowl, using an electric hand-held mixer), briefly blend the flour, sugar, cocoa, baking powder, baking soda, and salt on low speed. Add the eggs, milk, oil, and vanilla and mix at low speed, scraping the bowl as necessary, until the mixture is thick and creamy, like chocolate frosting, about 5 minutes. With the mixer running, gradually add the hot coffee, mixing at low speed just until combined. The batter will be quite thin. Divide the batter equally among the pans.
Bake, switching positions and rotating the pans halfway through, until a tester inserted in the center of the cake comes out with only a few crumbs clinging to it and the center feels firm to the touch, 20 to 25 minutes. Let the cakes cool completely in the pans on racks.
Make the coffee-whiskey whipped cream
Clean and chill the mixing bowl and whisk attachment. In a measuring cup, stir the instant espresso into the whiskey until completely dissolved. In the chilled bowl, whip the cream, brown sugar, and whiskey mixture on medium-high speed until medium peaks form, 2 to 3 minutes.
Finish the cake
Run a thin knife around the inside edge of the cake pans and turn the cakes out onto a large cutting board; peel off the parchment.
Transfer one layer to a cake plate and spread a third of the whipped cream on top, leaving a 1/2-inch border; repeat with the second layer. Put the top layer in place and spread the remaining whipped cream out to the edge.
To make the chocolate shavings, put a piece of waxed paper or foil on a baking sheet. Microwave each block of chocolate on medium power for 20 to 30 seconds to soften slightly, then draw a vegetable peeler along the chocolate bar’s edge, letting the curls fall onto the waxed paper. Make enough curls of both colors to top the cake generously, 1-1/2 to 2-1/2 oz. each. Refrigerate the shavings to make them easier to handle.
Arrange the shavings on top of the cake and serve.
Make Ahead Tips
The baked cake layers can be wrapped in plastic and kept at room temperature for 1 day.
The assembled cake will hold for 2 hours in the refrigerator.