Put the butter in the freezer 20-30 minutes before mixing.

Sift the flour with the baking powder, salt, and vanillin into a bowl, add the sugar, and mix.

Grate the cold butter on a coarse grater and quickly rub the dough by hand into shortbread crumbs. Put the crumbs in the fridge.

For the filling, blend the cottage cheese, sugar, vanilla sugar, eggs, and sour cream until smooth (don't add the berries yet).

Line an 18 cm springform pan with parchment and brush the sides with vegetable oil. Pour in most of the crumb mixture for the base, press down, and form small edges.

Pour in half the cottage cheese filling, scatter the blueberries on top, then pour in the rest of the filling. Sprinkle the remaining crumb over the pie without pressing down.

Bake for 60 minutes in a well-preheated 180 °C oven.

Let the pie cool completely and chill in the fridge overnight.