1. Preheat the oven to 375F (190C) with fan or gas 5. Place the ground beef in a shallow roasting pan, breaking it up. Roast for 5 minutes. Take the beef out and stir it, then add the star anise and cloves (tie them in a piece of muslin cloth first, if desired) and roast for another 10 minutes. Stir again and continue roasting for 30-40 minutes, or until the beef is crispy and dark brown. Stir and scrape the bottom of the pan a few times as needed. Set aside.
2. Meanwhile, heat the oil in a large saucepan over medium heat and cook the pancetta for 8-10 minutes, or until crispy and browned on all sides. Add the onions, carrots, celery and garlic and cook for 8-10 minutes, or until the vegetables have softened. Stir in the mushrooms, oregano and bay leaves, then sprinkle with sugar and tomato paste. Stir well, then add the wine and vinegar and bring to a boil. Simmer for a few minutes, or until the liquid has reduced by about a third.
3. Add the tomatoes, a can of water, the stock pot or cube, stir well and bring to a simmer. Add the roasted ground beef and spice bag, season to taste, then reduce the heat to low and simmer for about 1 hour and 30 minutes, or until the sauce is thick and glossy. Taste and adjust seasonings as needed. The sauce will taste even better if allowed to cool completely and chilled for a day or two before reheating. Serve with pasta and grated parmesan, if desired.