For the filling: pass the cottage cheese through a sieve.
Mix together with the grated mozzarella, egg and salt.
Brush each sheet of fillo with yogurt, add filling to one edge and roll.
Transfer onto a tray lined with parchment paper, spread with butter (20 grams) at room temperature, mixed with egg yolk, and bake for 30 minutes at 170°C. (Optionally, sprinkle with sesame seeds.)
