* 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.