Bring 6 quarts water to a rolling boil. Salt aggressively (sea-salty).

Heat your widest sauté pan (14-inch) over high for 2 minutes. Add 4 tbsp butter. When foaming subsides, add ALL mushrooms in one layer. Do NOT stir for 4 full minutes — let them sear golden.

Toss mushrooms, cook another 3–4 minutes until deeply browned and liquid evaporates. Season with ½ tsp salt. Push to the edges.

Drop fettuccine into the boiling water now. Set timer for exactly 8 minutes (it will finish in sauce).

Add remaining 3 tbsp butter + paper-thin garlic to the center. Cook 45–60 seconds until garlic is pale golden. Pour in white wine — sizzle! Scrape up every brown bit and reduce by two-thirds (2 minutes).

Remove pan from heat completely. Pour in cold heavy cream and stir — this tempers it. Return to medium-low and simmer gently 2 minutes.

Reserve 2 full cups pasta water. Using tongs, transfer pasta directly into the sauce (some water clinging is perfect).

Add ¾ cup pasta water, all the Parmigiano, and Pecorino in 3 batches while tossing vigorously with tongs for 2 full minutes over medium heat. The sauce will transform from watery to glossy and thick. Add more pasta water ¼ cup at a time until it perfectly coats each strand.

Remove from heat. Add nutmeg, a final 1 tsp raw butter, half the parsley, and tons of cracked pepper. Toss once more. Let rest in warm pan 5 minutes — sauce will settle into pure velvet.

Twirl into warmed bowls, shower with extra cheese, remaining parsley, more pepper, and optional crispy mushroom chips or a drop of truffle oil. Serve immediately with chilled Pinot Grigio and zero conversation for the first three bites.