12 tablespoons unsalted butter , cut into 12 pieces; 6 ounces bittersweet chocolate , chopped; 1 teaspoon vanilla extract; 4 large eggs, separated; 1 cup (7 ounces) granulated sugar, divided https://www.thatskinnychickcanbake.com/italian-flourless-chocolate-cake https://www.americastestkitchen.com/episode/658-savory-and-sweet-italian