January 26th, 2017
Preheat oven to 350˚F. Butter 3 (8″ x 2″) round cake pans and line bottoms of each with parchment paper. Butter paper and dust pans with flour, knocking out excess.
Whisk together boiling water, coffee and cocoa powder in a bowl until smooth, then whisk in milk and vanilla. Sift together flour, baking soda, and salt in another bowl.
Beat together butter and sugars in a large bowl with an electric mixer until pale and fluffy, then add eggs 1 at a time, beating well after each addition. Beat in flour and cocoa mixtures alternately in batches, beginning and ending with flour mixture (batter may look curdled).
Divide batter among pans. Tap pans on the counter to remove any large bubbled and smooth tops with an offset spatula. Bake in upper and lower thirds of oven, switching position of pans halfway through baking, until a tester comes out clean and layers begin to pull away from sides of pans, 20 to 27 minutes total. Cool layers in pans on racks for about 20 minutes, then invert onto racks, remove parchment paper, and cool completely.
Make icing: Melt chocolate in a large metal bowl set over a saucepan of simmering water, stirring occasionally. Remove bowl from heat, then whisk in sour cream and liqueur. Cool to room temperature, stirring occasionally (frosting will become thick enough to spread).
Put 1 cake layer, rounded side up, on a cake plate and spread with about ½ – 1 cup icing. Top with another cake layer, rounded side up, and spread with another layer of icing. Top with remaining cake layer and frost top and sides of cake with remaining icing. * Alternatively, you can top this cake with sweetened whipped cream or chocolate whipped cream in a pinch – the chocolate cake will really shine through then.