Grate the onion. Soak the bread in water and then squeeze by hand. Mix the grated cheese, grated onion, the ground meat, salt, pepper, bread and egg yolks. Knead the mixture thoroughly. Make balls of meat, the size of walnuts, then roll them into a cocoon shape. Roll them in the flour, then in the egg white. Fry them in oil. Serve with fried potatoes.