I don’t think you’ll find a stronger marriage than Kahlua and chocolate, and this spectacular layer cake proves that point in just one bite. This deep dark cake is for adult palates, and it makes perfect dinner party fare. Should you want to temper its flavor a bit, reduce the Kahlua to 1/2 cup and increase the buttermilk to 1 cup. Serve freshly made with a steaming cup of coffee.