Preheat oven to 450 degrees.
Melt the chocolate and butter together. Cool slightly.
Meanwhile, in a bowl, whisk together the yolks and eggs.
Mix in the powdered sugar.
Whisk into chocolate mixture, then whisk in flour.
Fill 12 greased 4 ounce foil tins with batter and refrigerate until ready to bake, or bake immediately.
Bake for 5 to 6 minutes from cold, or 4 to 5 minutes from room temperature.
Turn out of tins immediately onto the plate.