Hoisin is a thick, glossy, near-black Chinese sauce that tastes sweet and salty at once, with a deep fermented-soybean savouriness, a hum of garlic and the warm five-spice perfume of star anise and fennel. Smooth and almost jam-like, it is brushed over char siu pork as a sticky red glaze, stirred into stir-fries, and set out as the dipping sauce for Peking duck, mu shu pancakes and spring rolls. Despite the name — hoi sin means seafood in Cantonese — it contains no seafood at all.