Towering Flourless Chocolate Cake

Name: Towering Flourless Chocolate Cake
Prep time: 35 min
Cook time: 50 min
Total time: 1 h 25 min
Cuisine: American
Ingredients: 2 1/2 sticks unsalted butter, cut into pieces, plus more for the pan; 6 ounces bittersweet chocolate, chopped; 6 ounces unsweetened chocolate, chopped; 6 large eggs; 3/4 cup turbinado sugar; Pinch of salt; 1/2 cup stout beer (such as Guinness); 1 teaspoon vanilla extract; 2 ounces semisweet chocolate, chopped; 2 tablespoons unsalted butter; 1 tablespoon light corn syrup; 1 cup granulated sugar; 3 large egg whites; 1/4 teaspoon cream of tartar; 2 teaspoons vanilla extract