This gorgeous chocolate cake is frosted with a coffee buttercream and decorated with a dark chocolate glaze for a show-stopping coffee and chocolate cake.
Preheat the oven to 325°F. Grease three 8-inch round cake pans, line each of them with parchment, grease the parchment and dust the pans and parchment with cocoa powder. Set them aside.
In a medium bowl, mix the cocoa powder, sour cream and hot water. Set aside for later.
In another medium bowl, whisk together the flour, baking powder, baking soda, and salt.
In the bowl of an electric mixer fitted with the paddle attachment, beat the butter and shortening on medium speed until it is light and fluffy.
Add the sugars to the bowl of the mixer and beat on medium speed until light and fluffy, about 5 minutes. Scrape down the bowl as needed.
Add the eggs one at a time, beating well between each addition. Add the vanilla, and beat well.
With the mixer on low, add the whisked dry ingredients alternately with the cocoa mixture, scraping the sides of the bowl as needed.
Give the mixture a last stir by hand before dividing among the three prepared pans.
Bake the cake layers for 30 to 40 minutes, or until a cake tester inserted into the center of the cake comes out clean. The cake will pull away from the sides of the pan when the cake is done.
Let the cake cool in the pans for 30 minutes before flipping them onto a wire rack to cool completely. Wrap them in plastic wrap to store them.
To make the coffee buttercream
Place the wrapped cake layers in the freezer while you prepare the buttercream.
In a medium saucepan, whisk together the sugar and flour. Whisk in the milk and cream, and cook over medium heat, whisking often until the mixture boils and thickens. This takes a good 15 minutes.
Transfer the thickened mixture to the bowl of an electric mixer fitted with the paddle attachment. Beat on high speed until the mixture is completely cooled, about 10 minutes (don’t just feel the bowl, check the mixture itself to be sure it has cooled!).
Reduce the speed to low and add the butter, mixing until it is thoroughly incorporated. Increase the speed to medium-high to make the frosting light and fluffy.
Add the vanilla and the espresso (or coffee extract) to taste.
To assemble the cake
Trim the cake layers so that they are flat and levelled.
Place one cake layer in the center of a serving plate. Place parchment strips to cover the exposed plate and catch any buttercream/ganache drips.
Top the first layer with 1 ¼ cups buttercream. Place the second layer over the buttercream, and repeat with another 1 ¼ cup of buttercream and the third layer.
Frost the top and sides of the cake with what’s left of buttercream. Place the cake in the fridge while you make the chocolate glaze.
To make the chocolate glaze
Place the chocolate, butter, and corn syrup in the top of a double boiler.
Stir the mixture with a small spatula until the ingredients have melted and the glaze is smooth.
Take the pan off the heat, and stir for a few minutes to allow the glaze to cool and thicken a little.
Finishing touches
Slowly pour the glaze over the top of the cake, pushing tiny droplets down the sides.
Let the glaze set for a few minutes before decorating the cake with a few chocolate pearls.
Refrigerate the cake for 20 minutes to set the glaze. The cake should be served at room temperature.