Put the onion, garlic, carrot, pepper, mushrooms and celery in big saucepan with the stock and chilli. Cover and simmer over a medium heat for about 10 minutes, until the carrots are tender. Uncover and simmer for 5 more minutes, until the liquid has almost evaporated.
Add the minced beef and cook until brown. Break apart the minced beef into small clumps with a fork. Add the chopped tomatoes, tomato purée and oregano and season to taste. Partially cover the pan and simmer for 35 minutes, until the sauce is thick and the vegetables are tender.
Serve with hot, drained, spaghetti and season with grated Parmesan or reggato.
