In a small cup (about 250 ml in volume), mix the lukewarm milk, sugar, yeast, and flour. Let the starter sit until it doubles in size.
Preparing the Dough:
In a bowl, mix the starter with sugar, flour, salt, egg yolks, oil, and lemon juice. Gradually add the oil and lukewarm milk and mix until the dough starts to pull away from the sides of the bowl. Let the dough rise in a warm place for about an hour.
Preparing the Curd Cheese Filling:
In a bowl, mix the curd cheese, egg yolk, and vanilla sugar. You can substitute this filling with poppy seeds or jam according to your preference. Chill the filling in the refrigerator.