Preheat oven to 400*, coat six muffin molds with 1 Tbsp. butter, then dust with cocoa powder making sure it is fully covered in the cocoa to prevent sticking. Tap out excess cocoa.
Stir the chocolate and remaining 2 sticks butter in a heavy medium saucepan over a low heat until smooth. With an electric mixer beat the eggs, egg yolks and sugar in a large bowl until pale and double in volume; 3-5 minutes. Fold in the melted chocolate mixture. Add the flour and whisk until smooth. Pour into the prepared molds.
Bake for 8-10 minutes until slightly puffed and just set around the edges. Let the fondants rest 3-4 minutes.