Melt butter, sugar and chocolate in a hot water bath. As soon as the mixture is liquid, separate the eggs. Beat the egg whites with a little salt until stiff. Mix egg yolk with hazelnuts and flour (becomes very crumbly).
Add the hot chocolate and fat mixture while stirring. Finally fold in the beaten egg whites with a hand whisk. Grease a springform pan (26 cm Ø) and sprinkle with rusk crumbs. Bake in the preheated oven (electric cooker: 175 °C/ gas: level 3) for approx. 35 minutes.
Leave to cool on a cake rack for about 1 hour. Whip the cream until stiff, add sugar, vanillin, sugar and cream setting agent. Sort the raspberries and carefully fold them into the cream, except for about 50 g.
Place the cake ring around the cake tin and spread raspberry cream on top. Chill for about 1/2 hour. Spread the remaining raspberries on the cake and decorate with mint, truffle and chocolate sticks.