Ingredients
Method
- Preheat the oven to 325°F. Grease and flour three 8-inch round pans, optionally lining the bottoms with parchment paper.
- Combine the yellow cake mix, all-purpose flour, sugar, and pudding mix in a mixer bowl and whisk to blend.
- Add the remaining ingredients to the bowl and mix on low speed for approximately 30 seconds.
- Scrape the sides and bottom of the bowl as needed and mix on medium speed for two minutes until the batter is well blended.
For the Chocolate Batter
- Dissolve 4 tablespoons of cocoa powder in 4 tablespoons of very hot water in a small bowl and let it sit for 3 minutes.
- Transfer two cups of yellow cake batter to a small bowl, add the cocoa mixture, and stir until well combined.
Filling the Pans and Marbling
- Divide half of the yellow cake batter among the three pans. Layer half of the chocolate batter on top, drizzling about 1/3 cup into each pan. Repeat with the remaining yellow and chocolate batters. Run a knife through the batter to marble, avoiding over-mixing, and tap the pans on the counter to level the batter.
- Bake at 325°F for 20-25 minutes until the layers spring back when touched or a toothpick comes out with a few moist crumbs.
- Cool the cake layers in their pans on a wire rack for 10 minutes before turning them out, ensuring they are completely cool before frosting.
For the Chocolate Buttercream
- Mix the butter on low to medium speed until smooth, then blend in the vanilla. Add the powdered sugar, salt, and cocoa powder.
- Add most of the milk and begin mixing at low speed to prevent the powdered sugar from dusting the kitchen.
- Continue mixing, adding the remaining milk as needed for 5 to 6 minutes until smooth. Adjust the consistency with additional milk or powdered sugar as necessary.
Assembling and Decorating
- Place the first cake layer on a base or pedestal and spread with chocolate buttercream. Repeat with the remaining layers and fill any gaps between them with frosting.
- Apply a thin layer of buttercream to the top and sides of the cake, then chill in the freezer for 15 minutes or the refrigerator for longer.
- Apply the final layer of frosting and decorate as desired. Smooth the sides with a bench scraper, add texture with an offset spatula, and pipe shells on top using a 1M tip, working from the outer edge toward the center.
Storing and Serving
- Store the cake in an airtight container at room temperature for up to two days before moving it to the refrigerator. Refrigerate immediately if the room is warm.
- Remove the refrigerated cake two hours before serving to allow the cake and frosting to soften to room temperature.
Notes
Freezing: These cake layers can be made in advance and frozen. After baking and cooling (we often wrap them while still a bit warm), place each cake layer on a foil-wrapped cake board and cover tightly with plastic wrap and foil. They will stay fresh in the freezer for three months!
When thawing, remove the layers from the freezer and place them on the kitchen counter (still wrapped). We usually remove the wrapping after about 30-45 minutes. Condensation will likely collect on the wrapping during that time.