Fold the veal in half and sew two sides together to form a bag. To make the stuffing heat the oil in a saucepan, add the onion and fry until soft. Stir in the spinach, sausage meat, egg, cheese and salt and pepper to taste. Stuff the veal with the mixture and sew up the open end. Place in a casserole dish and dot with the butter. Cover and cook in a preheated moderate oven, 160C gas mark 3, for 2 hours, turning once. Remove the thread and slice the veal. Seve hot, with the pan juices poured over, or cold with salad.
