Melt the butter and let it cool down a little. Roughly chop the chocolate and walnuts. Mix flour, sugar, espresso, 100 cocoa, baking powder and vanilla sugar in a bowl. Place the eggs in a mixing bowl and whisk until creamy. Allow butter to run in and stir in. Mix in the flour mixture well with a mixing spoon. Stir in crème fraiche, then fold in chocolate and nuts.
Pour the dough into a greased, floured fat pan of the oven (approx. 35 x 40 cm). Brush smooth. Bake in the preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: level 2) for 25-30 minutes. Let cool in the fat pan on a cake rack. Mix cream cheese and icing sugar until creamy with the whisk of the hand mixer. Spread the cream cheese and icing sugar on the cake, dust with approx. 1 tbsp. cocoa and cut into small pieces
waiting time approx. 2 hours