Fettuccine al burro e panna (fettuccine Alfredo)

For ➍
40 cl heavy cream*
80 g (6 tbs) unsalted butter
240 g Parmesan or Asagio cheese, grated
1 ts salt
fresh-ground black pepper
pinch of fresh-ground nutmeg
400 g very thin fettuccine pasta**

Combine the butter and 30 cl of the cream in a large pan. (It must fit the sauce and the pasta.) Heat over a low flame, stirring frequently, until the butter is melted and the cream comes to a bare simmer. Remove the pan from the heat once the butter is evenly incorporated into the cream. Avoid cooking.***
Cook the pasta, draining it before it reaches the al dente stage (3 m). (The pasta should be slightly undercooked because it will continue to cook while the sauce is being finished.)
Drain the pasta and add it to the pan, along with the remaining cream, the cheese, the salt, the nutmeg, and several grinds of the pepper mill.
Heat the pasta and sauce over a low flame, tossing continuously, until the cheese melts into the sauce and the sauce thickens slightly, about 1 to 2 m.

*There are several versions of this recipe, some with cream deleted, and with equal portions of butter and cheese (150 g). The cheese is melted in the soft butter until smooth.
**Fresh if possible. All thin pasta, like tagliatelle, will do.
***Try a quick & innovative way of cooking.
This recipe was created in Rome in 1914 by Alfredo Di Lelio for his pregnant wife. It refers to a traditional way of making butter sauces for pasta, but the cook doubled the quantity of butter. It become popular in the US after some Hollywood stars ate the dish in Rome and brought it back home, where it became known as Fettuccine Alfredo. The original restaurant is still a tourist restaurant in Rome. The family opened a new Alfredo's and franchised restaurants in the US, proudly bearing the image of the master, as seen in the picture.
Americans tend to add chicken or shrimps. This is really a primo piatto, a first course, to be followed by something substantially meaty or fishy.