Meat sauce for ravioli, lasagna, pasta

On a layer of pancetta (or lard) cut very thin, put a thinly sliced onion, pieces of carrot and celery, parsley, rosemary, alloro, soaked dried mushrooms (or fresh), some pieces of beef, clippings of veal and chicken, and a few pieces of sausage. Add salt to taste and some small flakes of butter. Cook over a very low heat, in a covered casserole, avoiding mixing, until the onion has started to color. Pour some white and red wine in and once this has evaporated, add a little tomato sauce. Leave to cook, diluting with warm water several times. The sauce must cook very slowly for several hours: then it is sieved to form a puree and put back on the heat with the butter (or cooking cream). The sauce must remain fairly liquid. Sieve once more and cool to eliminate the fat. Then put back onto the heat if necessary with the addition of some water and a little butter. Cook for a few minutes so as to make it piping hot to dress the pasta.