Place the mushrooms in a small saucepan and cover with the stock (or water); bring to a boil. Lower the heat and simmer on very low heat to reconstitute (or pour 1 cup boiling water over them, cover and let stand for 10 minutes).
Bring a large pot of water to a boil, salt it, add the pasta and cook until al dente. Drain, reserving 1 cup of the pasta cooking water.
While the pasta is working in a heavy pot, heat the EVOO, 2 turns of the pan, over high heat until smoking. Stir in the veal to brown slightly, then stir in the sausage, crumbling the meat. Add the carrot, celery, onion, garlic and sage; season generously with salt and pepper. Cover and cook the vegetables, stirring occasionally, until softened, 3 to 5 minutes. Stir in the wine to deglaze, scraping up the browned bits from the bottom of the pan.
Remove the mushrooms from their soaking liquid and chop. Stir into the ragu with their strained liquid. Stir in the milk, lower the heat to medium-high and cook to thicken.
Stir the reserved 1 cup pasta cooking water into the ragu. Add the pasta and toss. Top with a liberal amount of cheese.