chocolate cake with whipped topping

the goods:

cake:
1 cup (2 sticks) unsalted butter, room temperature, plus more for pans
2 cups all-purpose flour
1/2 cup unsweetened cocoa powder
1/2 teaspoon baking powder
1/2 teaspoon baking soda
1 teaspoon salt
1 and 1/2 cups sugar
2 large eggs plus 3 large egg yolks
2 teaspoons pure vanilla extract
1 cup buttermilk

whipped frosting:
3 large egg whites
3/4 cups sugar
1/4 teaspoon pure vanilla extract



Preheat oven to 350 degrees. Butter and dust with cocoa powder two 8-inch cake pans, tapping out excess powder. In a medium bowl, whisk flour, cocoa powder, baking powder, baking soda, and salt.

In a large bowl, using an electric mixer, beat butter and sugar until light and fluffy. With mixer on low, beat in eggs and yolks, one at a time. Beat in vanilla. Alternately beat in flour mixture and buttermilk, beginning and ending with flour mixture; mix just until combined.



Divide batter between pans; smooth tops. Bake until cakes pull away from sides of pans, 32 to 35 minutes.



Let cool in pans 10 minutes. Run a knife around edges of pans and invert cakes onto a wire rack. Let cool completely.



While cakes cool, make whipped topping: In a heatproof bowl set over (not in) a saucepan of simmering water, combine egg whites, sugar, a pinch of salt, and 1/3 cup water. Cook over medium, stirring constantly, until sugar has dissolved, 2 to 3 minutes. Transfer to a large bowl. Using an electric mixer, beat on medium-high until glossy, stiff peaks form; reduce speed to low and add vanilla. Beat just until combined.



Place one cake, bottom side up, on a cake stand or platter. Spread top with whipped topping. Top with remaining cake; frost top, then sides. Top with shaved dark chocolate. Serve within a few hours.