Grease a springform pan (26 cm Ø) and dust with flour. Coarsely chop the chocolate and nuts separately. Dice butter and melt with half of the Scho kolade in a hot water bath. Stir in sugar, 1 packet of vanillin sugar and 1 pinch of salt and let it cool down for about 5 minutes.
Mix the eggs individually into the butter-chocolate mixture. Stir in crème fraiche. Mix flour and baking soda and stir in briefly. Fold in nuts and the rest of the chocolate. Spread into the mould. Bake in the preheated oven (electric oven: 175°C/circulating air: 150°C/gas: level 2) for 35-40 minutes (the cake base remains juicy and slightly moist inside).
Remove from the edge of the mould and allow to cool in the mould.
Wash and clean the strawberries and, depending on size, cut them in half or quarters. Sort and wash the blueberries. Whip the cream until stiff, pour in 2 sachets of vanilla sugar and cream firming agent.
Remove the cake base from the mould. Place on a cake plate, enclose a cake ring around it. Spread cream on top. Mix the berries and spread on top. Press something into the cream to give them enough hold.