National Vichyssoise Day is observed worldwide every November 18 and celebrates the thick, creamy soup known as vichyssoise. This soup, believed to have origins in either America or France, is made from chicken stock, cream, and pureed vegetables such as leeks, onions, and potatoes. It is typically served cold but can also be enjoyed hot. The soup is named after the French town of Vichy, and its creation is often attributed to Louis Diat, a French chef at the Ritz-Carlton in New York City, who is credited with reinventing it in the United States. To celebrate this food holiday, individuals can prepare vichyssoise at home by sautéing leeks and onions, adding potatoes and chicken stock, and then pureeing the mixture before incorporating heavy cream.