This is the original and best version of this much-loved sauce. It requires a great many ingredients and a lot of time, but it is worth all the effort. Use it to fill cannelloni, to dress plain boiled pasta or to layer in Lasagne. It freezes very well for up to 6 weeks.
Heat the oil and fry the onion, carrot, celery and garlic together until the onion is soft and transparent. Add the prosciutto or bacon, stir and simmer for about 4 minutes. Then add the drained mushrooms (if using) and the beef. Brown the beef carefully, without letting it go crisp, then pour in the wine and raise the heat to evaporate the alchohol. Pour in the diluted tomato purée and stir ca