A chilled leek and potato soup, often tinned, always excessively creamy, featured on virtually every summer menu in mid-1970s Soho, but its origins go back much further. Louis Diat, the chef at New York’s Ritz Carlton Hotel, claimed to have invented it in the 1930s saying, as all French chefs do, that it was inspired by his mother’s Potage bonne femme. Anywhere other than the States it could only be made in winter, as leeks were, and remain to this day, a strictly winter vegetable. The Yanks of course have no truck with something so silly as nature’s natural cycles and grow everything all year round. Diat probably didn’t invent the soup but he got to name it after his home town, Vichy (not as some experts claim because it should be made with Vichy water). What is unarguable is that the soup is a classic.

I wasn’t aware of the seasonal nature of leeks on the morning of my first day as a professional chef, when this soup was the first dish, on the first menu, of my short career. A shopping expedition to Berwick Street market produced no leeks and considerable panic. A phone call to my mother put me straight on the stupidity of using leeks in summer, but she did suggest that I try spring onions instead. Another sortie, this time to Chinatown, resulted in me finding enormous green spring onions and these were what I used to make the Vichyssoise. Leeks are in the shops all year round these days, but I suggest you avoid them in summer as they have woody cores and a sour taste. All vegetables have natural seasons which cooks ignore at their peril.