Vanilla Cake Batter Ingredients:
- 2 3/4 cups sifted cake flour
- 2 tsp baking powder
- 1/2 tsp baking soda
- 1 tsp salt
- 3/4 cup unsalted butter, room temperature
- 1 1/2 cups granulated sugar
- 2 large eggs + 2 large egg whites, room temperature
- 1 Tbsp pure vanilla extract
- 1/2 cup sour cream, room temperature
- 1 cup whole milk, room temperature
Chocolate Cake Batter Ingredients:
- 1/4 cup sifted unsweetened natural cocoa powder
- 1 1/2 Tbsp granulated sugar
- 1 1/2 Tbsp whole milk, room temperature
- 3/4 tsp instant coffee or espresso powder (optional)
Chocolate Buttercream Ingredients:
- 2 Cups unsalted butter, room temperature
- 6 Cups powdered sugar
- 1 cup natural unsweetened cocoa powder
- 6 Tbsp whole milk, room temperature
- 4 tsp pure vanilla extract
- 1/4 tsp salt
Instructions:
1. Preheat the oven to 350°F/177ºC. Prepare cake pans with parchment paper circles.
2. Combine cake flour, baking powder, baking soda, and salt in a bowl.
3. Beat butter, sugar, eggs, egg whites, vanilla, and sour cream in a stand mixer until light and creamy.
4. Gradually add dry ingredients and milk, mixing until just combined.
5. Divide batter into vanilla and chocolate portions.
6. Spread batter in cake pans and swirl to create marbling.
7. Bake for 30-35 minutes until a toothpick comes out clean. Let cakes cool in the pan for 5 minutes.
8. For the chocolate buttercream, whip butter until creamy, then mix in powdered sugar, cocoa powder, milk, salt, and vanilla until smooth and uniform.
9. Once cakes are completely cooled, level them and apply a layer of chocolate buttercream. Fill and stack with chocolate buttercream, and crumb coat, and refrigerate for at least 30 minutes.
10. Frost the cake with chocolate buttercream, use a cake comb for texture, and let it set in the refrigerator for 30+ minutes.
11. Pipe chocolate buttercream swirls on top and adorn with marbled chocolate decorations.