Ingredients For the chocolate cake: 3/4 cup (65 grams) unsweetened cocoa powder 2/3 cup (150 grams) sour cream 1 1/4 cup (296 ml) hot coffee or water 2 2/3 cup (320 grams) all-purpose flour 2 teaspoons baking powder 1 teaspoon baking soda 1/2 teaspoon salt 1 1/4 cup (280 grams) unsalted butter, at room temperature 1 cup (215 grams) brown sugar 1 1/2 cups (300 grams) sugar 3 large eggs 1 tablespoon vanilla extract For the coffee buttercream: 1 1/2 cup (300 grams) sugar 1/3 cup (40 grams) flour 1 1/4 cup (295 ml) whole milk 1/3 cup (80 ml) heavy cream 2 tablespoons instant espresso powder 1 1/2 cups (340 grams) unsalted butter, at room temperature and cubed 1 tablespoon vanilla extract For the ganache: 8 ounces (227 grams) dark chocolate, chopped or use chips 3/4 cup (170 grams) unsalted butter, cubed 1 tablespoon light corn syrup Instructions To make the chocolate cake: Preheat oven to 325 degrees F. Line two 8-inch round cake pans with parchment paper and grease with non-stick cooking spray or coat with butter and flour. In a medium bowl, whisk together the cocoa, sour cream and hot coffee or water until smooth. Set aside to cool. In a separate bowl, combine the flour, baking powder, baking soda, and salt. In the bowl of stand mixer fitted with a paddle attachment, beat the butter and sugars together on medium high speed until very light and creamy, scraping the bowl down as necessary, about 5-7 minutes. Add the eggs one at a time, mixing after each. Add the vanilla. Add the flour mixture in 3 additions, alternating with the cooled cocoa mixture, ending with the flour mixture. Mix until just combined. Divide the batter equally between the prepared cake pans. Bake, rotating halfway through. until the center of the the cakes bounce back when touched and a toothpick inserted into the center comes out with a few moist crumbs, about 40-45 minutes. Let cool in the pans for 10 minutes, then remove to a wire rack to cool completely. To make the coffee buttercream: Whisk together the sugar, flour, milk, heavy cream and espresso powder in a medium saucepan. Set over medium heat and bring to a boil, stirring occasionally. Continue to cook, stirring constantly, until mixture is thickened, about 8-10 minutes. Pour mixture through a mesh strainer into the bowl of a stand mixer fitted with a paddle attachment. Beat on medium high speed until cooled to room temperature, about 10 minutes. Reduce the mixer speed to medium and add the cubed butter a tablespoon at a time, letting it become incorporated before adding the next tablespoon. Once all the butter has been added, add the vanilla and beat on high speed until buttercream is thick and creamy. If buttercream is too soft, chill in the fridge for 10 minutes, then try beating again. To assemble the cake: If desired, cut the cooled cake layers in half, creating 4 layers. Place the first cake layer on a cake stand or plate. Cover with 3/4 cup of the buttercream and top with another cake layer. Repeat. Cover the layer cake with a thin layer of buttercream to create a crumb coat. Chill cake for 10 minutes to set, then cover with remaining buttercream. Chill for at least 30 minutes. To make the ganache: Place the chopped chocolate, cubed butter, and corn syrup in a large heat-proof bowl set over a pan of barely simmering water. Stir as mixture melts. Once smooth, remove from heat and let cool for about 5 minutes. Pour about 1/2 cup of the ganache over the top of the chilled cake, spreading it just to the edge without letting it spill over the sides. Chill 5 minutes. Pour another 1/2-1 cup of the ganache over the cake, this time pushing it over the sides and letting it drip down. Let cake set for 30 minutes at room temperature or 10 minutes in the fridge before serving.