1 Pound of semisweet chocolate, coarsely chopped
10 Tablespoons (1 1/4 sticks) salted butter
5 Eggs, separated, room temperature
Melt chocolate and butter in double boiler over gently simmering water; stir until smooth. Remove from heat and cool.
Preheat oven 375 degrees. Generously butter a 9 inch springform pan. Beat yolks to blend. Stir into cooled chocolate. Beat whites to stiff peaks and gently fold 1/4 of whites into chocolate to lighten. Fold in remaining whites. Pour batter into prepared pan. Bake 12 minutes; do not over bake (cake will be loose). Cool completely in pan.