ready in 2 h. 55 min.
Put the flour into a bowl and crumble the yeast into the middle. Mix the yeast with a little lukewarm milk, a little of the flour and the sugar. Cover and leave to stand for about 20 minutes. Then add the melted butter, salt and the rest of the milk and knead to a pliable dough. Cover and leave to rise for 30 minutes. Knead well on a floured work surface and leave to rise for a further 30 minutes.
For the filling, grate the hard cheese and mix smoothly with the Sulguni cheese, quark, crème fraîche and egg. Add the chopped herbs and season well with salt and pepper.
Heat the oven to 180°C with fan.
Then, knead the dough once more and roll out to a circle. Butter the tin and line with the rolled-out dough, allowing about 15 cm to hang over the edge. Spread the filling on the dough and fold the overhanging dough over the filling in even folds. Press the edges together in the middle and brush with egg white. Bake in a preheated oven for 40-50 minutes, until golden brown. Take out of the oven, leave to cool for a short while, then take out of the tin and leave to cool until lukewarm. Then serve.