This quick and meaty sauce is a terrific version of the classic. Slideshow: Meaty Pastas
Cover the porcini with boiling water and let stand until softened, about 20 minutes. Drain the mushrooms, reserving 1/4 cup of the soaking liquid. Finely chop the porcini.
Meanwhile, in a large saucepan, heat the oil until shimmering. Add the veal, pork and a generous pinch each of salt and pepper; cook over moderate heat, breaking up the meat with a spoon, until barely pink, about 7 minutes. Add the onion and rosemary and cook until the onion is softened and just starting to brown, about 7 minutes.
Add the garlic and chopped porcini to the meat and cook until fragrant, about 2 minutes. Add the wine and the 1/4 cup of porcini soaking liquid and cook, stirring occasionally, until almost evaporated, about 5 minutes. Add the stock and marinara sauce and bring to a boil. Cover partially and cook over moderately low heat until slightly reduced, about 7 minutes. Stir in the parsley and 2 tablespoons of the grated cheese. Transfer to a bowl and garnish with the remaining 2 tablespoons of grated cheese.
The sauce can be refrigerated for up to 2 days.
Polenta By the Yard.