Sieve the flour and baking powder into a bowl. Add sugar, butter, vanilla sugar, salt and eggs and mix to crumbs. Put them into a springform pan and press them down well. Bake at 175° for about 15 minutes.
Let it cool down. Place the base on a cake plate and fold over a cake ring.
Mix the cream cheese with the icing sugar and spread on the base. Whip the cream with 2 P. vanilla sugar and 2 P. cream stiff and spread it on the cream cheese. Drain the blueberries and press them gently into the cream (collect the juice).
Mix 1/4 l blueberry juice with the cake glaze and 1 P. vanilla sugar, bring to the boil and pour over the blueberries while still hot. This creates a "marble pattern". Chill immediately. This cake also tastes very good with morello cherries.