Bring a large pot of water to boil for the pasta, stuffed pasta or gnocchi.
If you are preparing mushrooms, sauté sliced mushrooms in olive oil, a couple of turns of the pan, over medium-high heat until tender and dark. Season with salt and pepper, and deglaze with slash of dry sherry or dry white wine.
If serving with speck, stack ham slices and cut into thin 1/4-inch strips. Separate with fingertips.
If serving with radicchio, thinly slice radicchio and sauté in a little olive oil over medium high heat. Season with salt and pepper, cook 3 minutes to tender-crisp then drizzle with a little aged balsamic vinegar.
For the fonduta, rub a small nonreactive pot with a cut clove of garlic. Add cream, milk or half-and-half and butter, bring to a boil then reduce heat to low. Season with salt, white or fine ground black pepper, nutmeg and thicken it a bit. Whisk in yolk, if using, tempering it by combining with a little warm milk and cream then adding it all back to pot.
Salt boiling pasta water then cook pasta to al dente. Reserve half a cup of starchy cooking water just before draining pasta.
Stir in cheese and season to your taste with salt, pepper and nutmeg.
Toss pasta with sauce and a bit of starchy cooking water. Serve immediately, mixing in any toppings or as-is, passing more cheese at table.