In a large mixing bowl, soak bread in enough milk to cover. With a pestle and mortar grind together fennel and pepper. Grind in garlic, thyme and salt. Pour off any excess milk from the bread and beat in eggs one at a time, until the bread is a smooth paste.
Grate cheese finely and stir into bread with spice mixture. Work in the meat with hands. Mince parsley and add to the mixture.
Using your hands, form into walnut-sized meatballs. Brown them thoroughly on all sides in hot olive oil, ¼ inch deep. Keep the meatballs warm in a slow oven.
Reserve ¼ cup of drippings. To it add minced onions and stir until lightly browned. Add purée and cook for two minutes, stirring constantly. Add chopped tomatoes including juice from the tin, stock and wine (use Chianti, Barolo, Rubesco, etc.) and stir until the sauce is well combined. Add oregano, sugar, and the basil leaves, finely minced. Stir well and add the meatballs.
Simmer gently but steadily for two to three hours. Every hour or so, add ½ cup more stock, wine or water. Take care to stir the sauce gently so as to minimize damage to the meatballs. Serve over steaming linguine or the pasta of your choice. The meatballs are unrivaled when used in Lasagna. If you prefer, rosemary may be happily substituted for oregano in the sauce. Mushrooms are always a happy addition.