While traditional ragù alla bolognese has a special place in my heart (and stomach), this mushroom variation is a delicious and satisfying alternative.  This recipe makes a generous eight cups of sauce, but is easily halved for a smaller yield.  The sauce can be made several days in advance, through step 5, refrigerated, and gently reheated before finishing with the cheeses and herbs.  For a traditional presentation, toss sauce with pappardelle or tagliatelle, adding a few spoonfuls of reserved pasta cooking water to thin the sauce as needed.