Preheat oven to 450°F. Butter and flour 4 (4 oz.) ramekins or custard cups. In the top 1/2 of a double boiler set over simmering water, heat the butter and chocolate until chocolate is almost melted.
Beat the eggs and egg yolks together until light colored and thick. Beat together the butter and chocolate. While beating slowly pour the chocolate mixture into the egg mixture and quickly add the flour and mix until combined. Divide batter between 4 moulds.
Bake for 6 to 7 minutes. The centers of the cake will still be quite soft. Invert on individual serving plates, let stand for 15 seconds, then unmold. Serve immediately with whipped cream.