Make the Royal pasta dough, rolling the sheets out to the thickness of a playing card. Set up the fettuccine attachment on your pasta machine and gently run through each pasta sheet. Place on semolina-dusted tray until needed.
Bring a large pan of salted water to the boil over a high heat, then add the fettuccine and cook for 1 to 2 minutes, or until al dente.
Meanwhile, make the sauce. Gently heat the cream in a large frying pan on a low heat, separate the egg yolk (save the white for another day) and whisk into the pan. Finely grate and gently whisk in the Parmesan, then season well with sea salt and black pepper.
Using tongs, drop the fettuccine into the sauce and toss well, adding splashes of the cooking water to loosen into a lovely, silky sauce.
Serve with shavings of truffle or gratings of nutmeg (if using), a good grating of Parmesan and a drizzle of truffle oil.