We mix flour with sugar, add chopped fat, egg yolks, lemon juice and milk and make a smooth dough, which we leave to rest in the fridge for an hour. In the meantime, we will prepare the filling. Rub the softened butter with sugar, eggs and lemon zest. While stirring constantly, add the curds and mix well. Clean the blueberries, wash them and let them drain. Roll out the prepared dough on a floured rolling pin into a sheet, which we carefully transfer with a rolling pin to a greased and filled mold (or to a baking sheet). Spread it with the prepared curd filling, smooth out the surface with palette knife, place the cake in the heated chamber of the combi oven and bake until the surface is slightly pink. Mix all the topping ingredients into a crumb and rub thoroughly with your fingers. Take the pre-baked cake out of the oven, spread it evenly with blueberries, lightly dust with vanilla sugar, sprinkle with crumbs and bake until pink.