Alfredo sauce
Fettuccine Alfredo is a pasta dish made with fettuccine, butter, and Parmesan cheese. As the cheese is mixed with freshly cooked, warm fettuccine and ample butter, it melts and emulsifies to form a smooth, rich cheese sauce coating the pasta. Originating in Rome in the early 20th century, it is now popular in the United States and other countries. Cream is commonly added to American versions, which are often served as a main course with optional chicken, shrimp, salmon or other ingredients on top or on the side. The dish is named for Alfredo Di Lelio, a Roman restauranteur who is credited with its invention and popularisation. Di Lelio's elaborate tableside service was an integral part of the dish. Fettuccine Alfredo is a richer version of the standard Italian fettuccine al burro ('fettuccine with butter'), also called pasta burro e parmigiano ('pasta with butter and Parmesan cheese'). It is a kind of pasta in bianco, that is, without added sauce. The Italian recipes do not include cream and are not topped with other ingredients, nor is the dish generally called "Alfredo" in Italy.
Source: Wikipedia