This pasta is from the region of Lazio, around Rome. Some sources believe the dish was developed at the end of World War II, when American soldiers stationed in Rome brought rations of eggs and bacon to Italian friends who turned them into this pasta sauce. Other sources suggest that it originated with coal miners (carbonari) in the region. It may be made with either pancetta or guanciale. Both are cured pork products: Pancetta is made from the pork belly, guanciale from pork jowl. Bacon (which, unlike guanciale, is smoked) is not commonly used in Italy. But it frequently appears in this dish in the United States.
The pancetta or guanciale should be cooked just to render the fat but not until crisp. The egg yolks, which serve as a liaison to thicken the sauce, are whisked with cream, then cooked with the spaghetti — to ensure that the sauce is hot — but only briefly; exposure to heat will eventually scramble the eggs and ruin the smooth consistency of the sauce. (Cream is not traditional but it is often used because it prevents the eggs from scrambling.)
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