The chef who won more Michelin stars than anyone in history made his name with a plate of mashed potato. The secret was that he put in a pound of butter for every two pounds of potato. Joël Robuchon was born in Poitiers in 1945, the son of a bricklayer. He went into a seminary at 12 to become a priest, and found he was happier helping the nuns in the kitchen. At 15 he was an apprentice cook. In 1981 he opened a small restaurant in Paris called Jamin. It won a Michelin star in its first year, a second the year after and a third the year after that. Nobody had ever done it so fast. The critics came for the lobster and the truffles, and went away talking about the mash. He used a small, waxy potato, boiled in its skin and pushed through a sieve. Then he stood over the pan and beat in cold butter, a cube at a time, until the potato could hold no more. At home the ratio was a quarter butter. In the restaurant it was nearer half. It went on the menu of every restaurant he ever opened, in Paris, Tokyo, Las Vegas and London. By 2016 they held 32 stars between them. He was named chef of the century, and for 13 years he was the face of French cooking on television. Robuchon could do anything with food. When he was asked what a cook should aim for, he said the simplest dish is usually the best. The modern mashed potato is also simple. It comes in a plastic tub, or as a packet of flakes you stir into hot water. The label lists rapeseed oil, skimmed milk powder and an emulsifier. The healthy recipe on the back suggests a splash of semi-skimmed and a scrape of low fat spread. It tastes of the tub. So there are two ways to treat the humblest vegetable in the kitchen. One of them won 32 Michelin stars, and it was the one with the butter in.