Wash the grapes, pluck them from the panicles and let them drain well. Mix the egg, 150 g sugar, vanilla sugar, oil and buttermilk with the whisk of the hand mixer. Mix 300 g flour and baking powder and stir in.
Heat the remaining raspberries, puree and pass through a sieve, squeeze out the gelatine and stir into the puree. Whip the rest of the cream until stiff, add vanilla sugar and spread on the cake. Let the raspberry puree cool down a little, put it into a small plastic bag, fold in a small corner of chopped grapes.
For the crumbles, chop the chocolate and melt it over a warm water bath. Knead butter, 125 g flour, 75 g sugar, cocoa and liquid chocolate into crumbles. Line the hollows of a muffin tray (12 hollows) with a paper baking tin each.
Spread the dough evenly into the moulds.
Spread the crumbles on the dough. Bake in the preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: see manufacturer) for 20-25 minutes. Remove from the oven, place on a cake rack and allow to cool.
Dust with icing sugar.