Lightly oil the bottom of a springform pan (26 cm Ø). Peel 50 g of the chocolate with a peeler into small rolls and chill.
Chop the rest of the chocolate and coconut oil coarsely and melt in a hot water bath. Put the rusk in a freezer bag and crumble finely. Mix well with the liquid chocolate and press into the mould. Chill for about 1 hour.
Soak gelatine in cold water. Select the blueberries, wash carefully and drain well.
Mix cream cheese, sour cream, sugar, vanilla sugar and lemon juice with the whisks of the mixer until smooth. Squeeze the gelatine and dissolve at low heat. Stir in 5 tbsp. cream cheese cream, then stir into the rest of the cream.
Immediately whip cream until stiff. First add the blueberries, then the cream to the gelling cream. Spread the blueberry cream on the crumb base. Cover and chill for at least 4 hours. Then sprinkle with chocolate rolls.