Pre-heat the oven to 80C. On the stove-top, put the oil and butter in a casserole, add the onion, garlic and star anise, and cook on a low heat for half an hour. Add the carrots and cook for 20 minutes. Add the celery, turn the heat down even lower and cook for a few minutes more. Now add the meat, gently pressing it down so it becomes integrated into the vegetables. Season generously, add the milk, then grate over a little nutmeg and cook very gently for at least half an hour, until the milk has just about disappeared. Add the wine and tomatoes, transfer the pot to the oven, cover, leaving the lid slightly ajar, and cook for at least six hours. (If during this time the meat is cooking dry, add a drop of water; also, fat will split and rise to the surface, but don't worry about it.) When the rag? has finished cooking, it should be rich and moist, but dry and not wet with liquid. Before tossing with the pasta, check the seasoning (be very generous with the pepper) and serve with freshly grated Parmesan.