All it takes to separate the fat from milk is 30 seconds of sloshing, so butter was no doubt discovered in the earliest days of dairying. It has long been important from Scandinavia to India, where nearly half of all milk production goes to making butter for both cooking and ceremonial purposes. Its heyday came much later in northern Europe, where throughout the Middle Ages it was eaten mainly by peasants. Butter slowly infiltrated noble kitchens as the only animal fat allowed by Rome on days of abstention from meat. In the early 16th century it was also permitted during Lent, and the rising middle classes adopted the rustic coupling of bread and butter. Soon the English were notorious for serving meats and vegetables swimming in melted butter, and cooks throughout Europe exploited butter in a host of fine foods, from sauces to pastries.