Peel and wash the vegetables, cut into pieces, put into a stewpot with the celery, parsley and tomatoes. Cook for 1 hour with 4 1/4 cups of cold salted and peppered water and 2 cubes of chicken stock. Chop the onions, gently fry them in olive oil for 5 minutes. Put the lamb through the food mill. Add to the onions, cook for 5 minutes. Pour the meat and onions into a bowl with the egg, a pinch of Cayenne and the white bread crumbs. Combine and make small balls. Keep aside. Pour the semolina into a salad bowl, add water according to the instructions, mix with your hands, adding the butter little by little, cover the semolina and keep warm in the top of a double boiler. Roll the meat balls in a little flour and fry in a frying pan with a little hot oil. Fry every batch for 5 minutes. Put the meat balls onto a dish covered with paper towel. To serve, pour the stock and the vegetables into a soup tureen. Place the semolina and the meat balls in a large dish. Harissa is traditional but very hot.