Martha's recipe is inspired by chef Jean-Georges Vongerichten's individual molten chocolate cakes, his signature dessert.
Preheat oven to 450 degrees. Butter and lightly flour four 4-ounce molds, ramekins, or custard cups. Tap out excess flour; set aside.
Place butter and chocolate in the top of a double boiler or heatproof bowl set over simmering water, and heat until the chocolate has almost completely melted. Meanwhile, beat together the eggs, yolks, and sugar until light and thick.
Beat in flour until just combined. Stir together the warm melted chocolate and butter. Pour chocolate mixture into the egg mixture. Divide batter evenly among the molds.
Bake the molds on a baking sheet for 7 to 8 minutes; the center will still be quite soft, but the sides will be set. Immediately invert each mold onto a plate, and let sit for about 10 seconds. Unmold by lifting up one side of the mold; the cake will fall out onto the plate. Serve immediately with whipped cream, if desired.