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 to a tray lined with paper, brush with room temperature butter (20 grams) mixed with egg yolk and bake for 30 minutes, temperature 170 °C, (sprinkle with sesame seeds if desired).
