Chocolate Stout Layer Cake with Chocolate Frosting

Name: Chocolate Stout Layer Cake with Chocolate Frosting
Ingredients: 3 ounces unsweetened chocolate, chopped; 2 1/4 cups all purpose flour; 2 teaspoons baking powder; 1 /2 teaspoon baking soda; 1 /2 teaspoon salt; 14 tablespoons (1 3/4 sticks) salted butter, room temperature; 1 1/4 cups plus 3 tablespoons sugar; 3 large eggs, separated; 3 /4 cup chocolate stout, regular stout, or porter; 2 /3 cup freshly brewed strong coffee; 1 pound bittersweet chocolate (54% to 60% cacao), chopped; 2 cups heavy whipping cream; 1 teaspoon instant espresso powder