* Place half of the butter in a serving bowl. Keep the bowl warm.
* Cook the fettuccine in abundant salted water. When the pasta is perfectly al dente, (firm but not too soft or overcooked), reserve a few tablespoons of the cooking water.
* Drain without shaking the colander too much, so that the pasta doesn’t become too dry. Drop the hot pasta in the bowl over the butter.
* Add the rest of the butter and toss quickly to melt it.
* Add the parmigiano reggiano cheese, and a small quantity of the reserved cooking water if the pasta appears too dry. Toss vigorously, and serve immediately, accompanied by a small bowl with more grated parmigiano reggiano cheese, for the guests to add if they would like.