In Italy, lentils are eaten as a symbol of good luck and prosperity because they resemble tiny coins. Tuscans eat lentils with "Cotechino", a large pork sausage. People in Bologna and Modena eat lentils with "Zampone", the sausage mixture stuffed into the skin of a pig's foot. In the Piedmont, little grains of rice symbolize money, so New Year's Day menus feature risotto.
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In the United States it seems most traditions come from the south. For example, a popular dish is collard greens, which symbolize greenbacks or money. Black-eyed peas are considered especially lucky and create wealth as they resemble coins. And corn bread is eaten because it resembles gold.