Chopping chocolate. Melt butter and chocolate in hot coffee. Separate one egg. Beat the egg white until stiff, pour in the starch and stir in. Beat two eggs, egg yolks and sugar with the whisk of the hand mixer for five minutes.
Stir in the flour and half of the chocolate mixture. Fold in the beaten egg white. Grease an earthenware pan (18 cm Ø) and sprinkle with sugar. Pour in the dough. Bake in the preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) for 15 to 20 minutes.
Sprinkle with brown sugar and place under the hot grill for another two to three minutes. Spread the rest of the chocolate mixture and crème fraîche on top and serve immediately.