Fry the meat in the oil for approx. 2 mins., dust with flour and remove. Sauté the onion, garlic, leek, carrots, celery and chili in the same pan for approx. 5 mins. Add the tomato puree and cook briefly. Pour in the wine and reduce completely. Add the tomatoes, the meat and stock, bring to the boil, then simmer for sauce approx. 30 mins.
Add the oregano before serving, season.
Cook the spaghetti in the salted water until al dente, drain and serve the with the sauce.