Three layers of moist and rich chocolate cake frosted with an incredible chocolate buttercream made with three kinds of chocolate.
PREP: Preheat the oven to 350 degrees F. Grease three 8-inch round cake pans generously with nonstick cooking spray. Line the bottom of the pans with parchment paper (Note 3), then spray the parchment paper with the nonstick spray. Set pans aside.
WET INGREDIENTS: In a medium bowl, whisk together the buttermilk, oil, and vanilla until combined.
DRY INGREDIENTS: In the bowl of a stand mixer fitted with the paddle attachment, mix together the flour, granulated sugar, cocoa powder (Note 1), baking soda, baking powder, and salt. With the mixer on low speed, add the buttermilk/oil mixture. Add the eggs, one at a time, and mix until well combined. Slowly add in the hot water (hot water "blooms" the cocoa powder making it more flavorful) and stir just to combine, stopping to scrape down the sides of the bowl with a spatula before mixing briefly again. Do not overbeat or overmix the cake or it will become dense.
BAKE: Divide the batter evenly among the three prepared pans and bake for 24 to 28 minutes, or until a cake tester comes out clean when inserted into the centers of the cakes. (My cakes are always done at 24 minutes).
COOL: Set the cakes on wire cooling racks to cool in the pans for 30 minutes. Turn out the cakes onto the racks to cool completely. (You can refrigerate or freeze the cakes at this time.) Do not frost cakes if not cooled completely.
BUTTERCREAM: In the bowl of a stand mixer fitted with the paddle attachment, beat the butter until creamy and lighter in color, about 3 minutes. Scrape down the bowl halfway through. Add the confectioner’s sugar (2 cups at a time) and then the cocoa. Mix on low speeds until just incorporated. Pour in the chocolate milk, vanilla, and salt. With the mixer on low speed, add the melted chocolate. Mix for an additional 2 to 3 minutes, until the buttercream is light and fluffy.
ASSEMBLE: If the cake layers are slightly domed on top, carefully level them off with a sharp serrated knife or cake leveler. To build the cake, place a tiny bit of frosting in the center of your cake stand (to keep the cake from sliding). Next place the first layer bottom side up on a flat plate or cake pedestal. Using a knife or offset spatula, spread the top of the cake evenly with buttercream. Place the second layer on top, top side up, and spread more butter cream evenly over the top. Repeat with the third layer and frost the top and sides of the cake. Decorate with chocolate shavings, sprinkles, or chocolate chips, if desired. Slice and serve.
BREAKING UP THE PROJECT: Since this is a bigger undertaking than other desserts, you can break up the project by making the cakes in advance. I like to do his so the cake has time to chill, which makes it easier to frost. Carefully wrap the cooled cake layers in plastic wrap and store them in the fridge for up to 2 days. You could also freeze them wrapped in plastic wrap for up to 1 month. Just defrost before frosting and assembling.
Note 1: the cocoa powder must be dutch process (not natural cocoa powder) for this cake. Otherwise it will end up overly dry and bland. See blog post for my recommendation on cocoa powder.
Note 2: coffee can be used in place if preferred
Note 3: Make a parchment paper round bottom for the cake pans by following the below steps: