8 oz. semi-sweet chocolate, cut into sm. pieces
1 stick unsalted butter, cut into sm. pieces
5 eggs, separated
A pinch of salt
2/3 c. sugar

Preheat oven to 325 degrees. Butter and flour a 9-inch round cake pan. Combine chocolate and butter and melt over hot water. Whisk together the egg yolks and all but 3 tablespoons of the sugar. Stir melted chocolate into egg yolks until thoroughly combined.

With an electric mixer, on medium speed, beat egg whites with a pinch of salt until soft peaks form. Gradually beat in the remaining sugar and continue to whip until egg whites are stiff but not dry.

Carefully fold chocolate mixture into egg whites. Pour into prepared pan. Bake for 1 hour 15 minutes. As the cake cools, the center will sink and crack. Dust the cake with powdered sugar and serve with unsweetened whipped cream.