Line the 24 cm springform baking tin with baking paper, finely crush the biscuits and melt the butter. Mix the melted butter with the biscuits and firmly press the mixture into the base of the springform. Then place into the refrigerator for at least half an hour.
Bring the blueberries, powdered sugar, vanilla sugar and lemon juice to a boil, remove from the stove and blend with a hand blender. Then, press the mixture through a fine sieve to remove all large pieces of fruit skin. Place aside and leave to cool at room temperature.
Whip the cream until stiff and stir in the cream cheese a spoon at a time. Place to one side.
Stir the gelatine into the cooled blueberry sauce and bring to the boil. Once the mixture is at a boil, remove from the stove. Carefully fold the warm blueberry sauce into the cream. Once the mixture has turned purple, pour it onto the prepared base and leave to cool in the refrigerator for at least 5 hours.
Take the cake out of the refrigerator before serving and use a sharp knife to loosen the edges before removing the springform ring. Decorate with blueberries as desired.