After pizza, spaghetti alla carbonara is probably Italy’s most famous dish, but also its most controversial. Everybody knows that this plate of bacon-and-egg pasta is supposed to have a rich, creamy, sauce, but few know the real secret of how to achieve it. Outside—and even inside—Italy, people often cheat and add a little (or sometimes a lot of) cream to get the right consistency. But to purists (and even not so purists), cream might as well come in bottles with the number 666 printed on the label. They will tell you, with a stronger than religious fervour, that it is not part of the original recipe. Nor, for that matter are peas.