Vichyssoise

Vichyssoise is leek and potato soup, cooked then puréed smooth and chilled before serving. It's a French-style soup most credibly traced to a French chef working in a New York hotel kitchen in the early twentieth century, not to the town of Vichy it's named after — and it's genuinely worth being upfront about that, since the name suggests a rustic French origin the soup most likely doesn't have.

What it actually is

Leek and onion soften slowly in butter without browning, then potato and stock join them to simmer until everything is completely soft. The whole pot purées until perfectly smooth, cream is stirred in to finish, and — this is the part that sets it apart from an ordinary leek-and-potato soup — the entire thing chills fully before serving rather than going out hot.

Served hot, this same soup is usually called potage parmentier or crème de poireaux; vichyssoise specifically means the same base served cold, which is also the twist that made it distinctive when it was introduced.

How it's served

• Well chilled, in a bowl or cup, never warm.
• With a scattering of chopped chives, the traditional garnish, on top.
• As a starter, especially in warmer weather when a cold soup suits the season.

Writing it on a menu

• Flag dairy; the cream finish carries it.
• Say plainly that it's served cold, since a guest expecting a hot leek-and-potato soup should know in advance.
• Note that the same base served hot goes by a different name, in case a guest prefers it that way.
• Mention the soup's likely American origin, a small point of honest history some guests find genuinely interesting given the French name.