Vatrushka (Russian Sweet Cheese Buns)

Method

1. 1Warm the milk to body temperature (about 37°C) and stir in the yeast, a pinch of the sugar, and a few spoons of the flour. Let it stand 10–15 minutes until foamy — this proves the yeast is alive.
2. 2Add the egg, remaining sugar, salt, and flour and knead into a soft dough. Work in the softened butter last and knead 8–10 minutes until smooth and no longer sticky.
3. 3Cover and let rise in a warm place 1–1.5 hours until doubled, then punch down and, ideally, let it rise a second time, about 45–60 minutes, until doubled again, for the softest crumb.
4. 4Divide into 10 balls of roughly 80 g, place on a lined tray seam-down, flatten slightly, cover, and let rest 15–20 minutes.
5. 5Make the filling: press the tvorog through a sieve until smooth, then mix with the egg yolk, the 3 tbsp sugar for the filling, vanilla sugar, and sour cream. If the tvorog is wet, stir in the semolina.
6. 6Press a wide well into each bun with a floured glass bottom and spoon in about 2 heaped tablespoons (50 g) of filling, dividing it all between the buns. Brush the dough rims with beaten egg.
7. 7Bake in an oven preheated to 190°C for 18–22 minutes, until golden. Don't overbake — long baking dries them out. Cool slightly before serving.