Put the butter in a medium bowl and melt it in the microwave. Add the chocolate and stir until melted.

Crack 2 eggs into a bowl, and add 2 more yolks. Add the sugar, and beat or whisk until light and thick, about 1 minute. Add egg mixture and 2 teaspoons flour to the melted chocolate; beat until combined.

Butter (well) 4-ounce ramekins and dust with cocoa powder. Tap out the excess. Divide the batter among the molds. (At this point you can refrigerate them for up to 3 hours; just bring themback to room temperature before baking.)

When youre ready to bake, heat the oven to 450. Put the molds on a rimmed baking sheet and bake until the cakes have puffed up a bit, the tops are barely set and the cakes still jiggle slightly when shaken, 7 to 9 minutes (better under-baked than overbaked). Let sit for 1 minute.

Put a plate on top of the ramekin and, with a potholder, carefully invert the cake onto the plate.Let it sit for 10 seconds, then lift up the ramekin. Serve immediately with ice cream or whipped cream or berries.