Line the bottom of the cake pan with parchment paper. Preheat the oven to 180°C (with convection).
In a food processor, mix all the ingredients for the crust until the dough forms a ball (you can also chop with a knife and quickly knead the dough by hand). Chill in the fridge for 45 minutes.
While the dough is chilling, chop the white chocolate and put it in a bowl. Heat 200g of heavy cream until almost boiling and pour it over the chocolate. After a while, stir until the chocolate melts and forms a smooth cream. Set aside.
Put the blueberries in a saucepan, heat until they melt and release juice. Strain through a sieve to remove the skins. Pour back into the saucepan and cook until there is about half a cup of thick liquid left (around 10 minutes). Let cool.
Take the dough out of the fridge, spread it on the bottom of the pan, and prick with a fork. Bake for 20 minutes at 180°C. Remove the crust from the oven, lower the temperature to 150°C, and turn off the convection setting.
In a large bowl, mix the quark and mascarpone. Add the cooled chocolate ganache, egg yolks, and blueberry puree. Mix well.
In a separate bowl, beat the egg whites until stiff. When they are ready, add a tablespoon of egg whites to the cheese mixture and mix vigorously with a whisk. Quickly fold in the remaining egg whites in batches.
Carefully pour the mixture onto the pre-baked crust. Bake for 60 minutes at 150°C until the top of the cheesecake sets (it may jiggle slightly when moved). After baking, let it cool in the open oven, then chill in the fridge overnight.
Remove the cooled cheesecake from the pan (use a sharp wet knife to separate the sides of the cheesecake from the pan). Beat the heavy cream with the powdered sugar and spread it on top of the cheesecake. Decorate with blueberries.
