Preheat oven to 450 F.
In one bowl, combine the butter and chocolate. Melt the mixture either in the microwave or on a double boiler.
In a separate bowl, combine the eggs, yolks, and sugar. Whisk until the color has lightened and the mixture is thick.
Add the egg mixture to the melted chocolate, along with the flour. Beat until combined.
Butter the ramekins, then sprinkle in cocoa powder, tapping out any extra.
Divide the batter equally among the molds. Place on a single baking sheet, and bake until the cakes have puffed a bit, but are only barely set, about 7 to 9 minutes.
Remove from oven and let rest on the tray for 1 minute. Hold a plate over the top of the ramekin, then turn the whole shebang over to carefully remove the cake from the ramekin.
Serve warm with fruit and / or ice cream.