What traditional white cheese fills a vatrushka pastry?

Tvorog is the traditional white cheese that fills a vatrushka pastry.

Vatrushka is an Eastern European ring-shaped pastry with an open center containing a sweet filling of tvorog, sometimes accompanied by raisins or pieces of fruit. The pastry is usually made from a sweet yeast dough and baked, although savoury versions use unsweetened dough and may include onion.

Tvorog is a soft, white fermented milk product made by fermenting milk and removing the whey. It resembles fresh curd cheese and is widely used across Central and Eastern Europe. Depending on the region and production method, it can be smooth, soft, or grainy, with different fat levels.

Ricotta and mascarpone are plausible distractors because they are also soft cheeses used in desserts, but they are not the traditional vatrushka filling. Bryndza is another regional white cheese, usually sharper and saltier. Vatrushkas are commonly about 5–10 centimetres across, though larger versions are also made.