No one is sure about the origins of bean curd. Legend says it was invented in the second century BC by Liu An, the king of Huainan; some argue that a stone relief excavated from a tomb of the same era depicts a bean-curd workshop. The earliest written reference to bean curd, however, is in a 10th-century text, and the Liu An legend only began a few hundred years ago, during the Ming dynasty. Some scholars have suggested that bean curd was first made by nomads who migrated south and hankered after their customary cheese; others that it was developed by a rural doctor who would have been familiar with soy milk and had gypsum in his medicine chest. All that is certain is that by the Song dynasty it had become a popular food.
'Flower' bean curd and firm white bean curd are just the most basic forms of this most versatile foodstuff. In the markets of Hunan, there are stalls piled high with a dozen different varieties. There are slices of golden smoked bean curd (la gan zi or xiang gan); treacly blocks of stewed aromatic bean curd of various kinds (lu dou fu or xiang gan); deep-fried bean curd puffs (you dou fu); 'hundred-leaves' sheets of leather-thin bean curd (bai ye); waffle-like 'dried orchids' that have been cut into trellis patterns and deep-fried (lan hua gan); and 'bound chickens' (kun ji), tightly tied rolls of thin bean curd that are used by Buddhists as a chicken substitute.
There is also fermented bean curd (dou fu ru), a chilli-laced relish that can be as sublimely rich and creamy as a high blue cheese. Fermented bean curd is eaten as a relish with rice congee or noodles for breakfast, or simply nibbled at the start of a meal, to whet the appetite - just a morsel on the tip of a chopstick is enough to send your taste buds wild with umami excitement. It is also used as an occasional seasoning in Hunanese cookery. Along with soy sauce, black fermented beans and winter-sacrifice beans, fermented bean curd brings to Chinese vegetarian food some of the rich and savoury tastes that one associates with meat and poultry.