Cook the fettuccine in plenty of salted water until al dente.
In the meantime, cut the butter into pieces and melt in a large saucepan at the lowest possible temperature. Salt, pepper and add a pinch of nutmeg.
When the pasta has finished cooking, remove a cup of the cooking water and keep it. Drain the pasta, add to the butter in the saucepan and mix well. Then, stirring constantly, add the grated Parmesan and gradually some of the cooking liquid until the Parmesan and butter emulsify and form a kind of cream sauce. The dish should be juicy, but not too soupy.
The most cooked pasta dish in the USA by Hollywood stars Pickford and Fairbanks.