Preheat oven to 450 degrees F (230 degrees C). Butter and flour four 4 ounce ramekins or custard cups.
In the top half of a double boiler set over simmering water, heat the butter and the chocolate until chocolate is almost completely melted.
Beat the eggs, egg yolks and sugar together until light colored and thick.
Beat together the melted chocolate and butter. While beating, slowly pour the chocolate mixture into the egg mixture, then quickly beat in the flour and mix until just combined.
Divide the batter between the four molds and bake at 450 degrees F (230 degrees C) for 6 to 7 minutes. The centers of the cakes will still be quite soft. Invert cakes on serving plates and let sit for about 15 seconds, then unmold. Serve immediately with fresh whipped cream, if desired.