Butter should be softened, then beat with cottage cheese, add pepper and salt to a homogeneous mass. Peel the potatoes and cut into extremely thin circles. Lubricate the form with butter and put a third of the potatoes in it, put the curd mass on top. Repeat the same calculation again and even out the surface with a damp spatula. Cover the mold tightly with foil and put in a heated oven to 200 C for 1.2 hours. Remove the foil and reduce the temperature to 190 C. Beat yogurt, egg, pepper and salt in a foam. Pour the resulting mixture onto potatoes and bake for another 20 minutes.