Twelve-Layer Mocha Cake Recipe

Ingredients

• 4 large egg yolks at room temperature 30 minutes
• 2 tablespoons whole milk
• 1/2 teaspoon pure vanilla extract
• 3/4 cup sugar, divided
• 1/2 cup all-purpose flour
• 1/4 teaspoon salt
• 2 large egg whites at room temperature 30 minutes
• 6 ounces fine-quality 60%-cacao bittersweet chocolate, finely chopped
• 1/4 cup water
• 5 large eggs, separated, at room temperature 30 minutes
• 1/2 cup sugar, divided
• 1 tablespoon unsweetened cocoa powder
• 2/3 cup hazelnuts (3 1/2 ounces)
• 3 large egg whites at room temperature 30 minutes
• 1/8 teaspoon salt
• 1/8 teaspoon cream of tartar
• 1/2 cup sugar
• 1/3 cup water
• 2 tablespoons sugar
• 1 teaspoon instant-espresso powder
• Coffee and mocha buttercreams
• Equipment: 3 (15-by 10-inch) 4-sided sheet pans (1/2 inch deep)