Sift the flour into a mound, make a well in the center and add the butter, cut into pieces, a pinch of salt and an egg yolk. Mix together, kneading and gradually adding sufficient water to obtain a smooth elastic dough. Shape into a ball, cover and leave to stand in a cool place for at least 1/2 hour. Roll out, folding the dough over on to itself a few times, as if making flaky pastry, then roll out into a thin sheet. Cut into circles about 3 inches in diameter. Dice the Mozzarella, cut the ham into pieces and place in a bowl with the 2 whole eggs, grated Parmesan, pinch of nutmeg and chopped parsley. Mix well, then spoon a little into the center of each circle. Brush the edges with beaten egg, fold over and press gently. Heat plenty of oil in a skillet. When hot, dip the crescents in beaten egg and then fry, a few at a time, until golden brown and puffed up. Drain well on paper towles and serve piping hot.