1-Getting started: Getting started with your high altitude marble cake begins by preheating the oven to 350°F (175°C) and preparing your baking pans. First, grease the bottoms of three 8-inch cake pans to ensure easy release. Mix the dry ingredients by sifting the flour, sugar, baking powder, and salt together in a bowl, then whisk them lightly for even distribution.

2-Mix wet ingredients: In another bowl, whisk the eggs, egg whites, buttermilk, melted butter, oil, and vanilla extract until well combined. Add the dry mixture to the wet ingredients and whisk just until everything comes together, about 10-15 seconds, to avoid overmixing. For that signature marble effect, reserve ¾ cup of the vanilla batter and stir in the cocoa mixture made by whisking 3 tablespoons unsweetened cocoa powder with 3 tablespoons hot water.

3-Layer the batters: Layer the batters in the pans: start with about ½ cup vanilla batter in each pan, top the center with 2 tablespoons chocolate batter, then add another ½ cup vanilla in the center of that. Repeat the layers until all batter is used, then gently swirl with a toothpick to create swirls without overmixing. Bake for 21-25 minutes, or until the tops spring back when touched and a toothpick inserted comes out clean. Let the cakes cool in the pans on a rack, loosely covered with a towel.

4-Assembling with Buttercream and Ganache: Once cooled, it’s time to assemble. For the buttercream, beat 2 cups softened unsalted butter until smooth, then gradually add 4 cups powdered sugar, 1 tablespoon meringue powder (if using), and ¼ teaspoon coarse kosher salt on low speed until thick. Mix in 2 teaspoons vanilla extract and whip on medium speed for 4-5 minutes until fluffy. Stack the cakes with buttercream between layers, apply a crumb coat, and chill for 30 minutes before frosting the entire cake smoothly.

5-Ganache preparation and finishing: For the ganache, warm 3 ounces heavy whipping cream until just simmering, then remove from heat and stir in 3 ounces chopped dark chocolate until smooth. Cool for 5 minutes, pour over the chilled cake, and spread gently to the edges for a drip effect. Let it set for 15 minutes, then pipe any reserved buttercream on top and decorate with macarons or chocolate pieces. This step-by-step approach ensures a professional finish that’s easy to follow at home.