Cream warm fat, 130 g sugar, 1 packet of vanilla sugar and 1 pinch of salt with the whisk of the hand mixer. Stir in the eggs one by one. Mix flour, cocoa and baking powder and stir into the dough alternately with the milk. Roughly chop the chocolate and fold in. Grease a springform pan (26 cm Ø) and sprinkle with breadcrumbs. Fill in the dough and smooth it down. Bake in the preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: level 2) for about 30 minutes.
Loosen the rim of the springform pan and let the cake cool down on a grid. Whip the sour cream, 20 g sugar and 1 packet of cream firming agent well with the whisks of the hand mixer. Whip the cream until stiff, adding 1 packet each of vanilla sugar and cream firming agent. Mix the sour cream and cream and spread on the cake like a dome. Select the berries and wash as required. Sprinkle on the cake and serve