In a small bowl, rehydrate the porcini in the 1/2 cup warm water for 30 minutes. Lift the porcini out with a slotted spoon and chop finely. Strain the liquid through a double thickness of damp paper towels to catch any grit. Reserve the porcini and liquid separately. Bring a large pot of salted water to boil over high heat. Meanwhile, heat the olive oil in a large skillet over moderate heat. Add the onion and sauté gently until softened, about 5 minutes. Do not let it color. Add the garlic and rosemary and sauté briefly to release their fragrance. Add the veal and pork and cook, breaking the meat apart with a wooden spoon, until it loses its pinkness. Season with salt and pepper. Add the porcini and cook until any moisture evaporates and the meat begins to sizzle. Raise the heat to moderately high, add the wine and 2 tbs reserved porcini liquid, and cook for a minute or two to evaporate the liquid. Add the stock and parsley and simmer briskly for 2 minutes. Add the Marinara Sauce or tomato puree, reduce the heat to gentle simmer, and cook for 3 to 4 minutes to blend the flavors. Keep the sauce warm while you cook the pasta. Add the pasta to the boiling water and cook until it is just shy of al dente. Set aside 1 cup of the pasta water, then drain the pasta. Return the pasta to the warm pot over moderately low heat. Add the sauce, stir well, and cook the pasta briefly so that it absorbs some of the sauce. Add the 2 tbs of Parmesan cheese and toss again, adding some of the reserved pasta water if the sauce appears dry. Transfer the pasta to a warmed serving bowl, garnish with a little additonal Parmesan, and serve at once. | 
