Sweet potato starch

Pure starch from potatoes — glossier and more set than cornflour, and the coating that gives karaage its crisp, crackly crust.

What to do with it

Classics built on it

FujianFuzhou fish ballsSmooth, springy balls of fish paste with a juicy pork filling, served in a light broth.No one here has made it yet FujianLychee porkCross-scored pieces of pork, fried until they curl up like lychees, in a glossy red sweet-and-sour sauce with water chestnuts.No one here has made it yet FujianOyster omeletteSmall oysters fried in a sweet potato starch batter with eggs — crisp in places, soft and gooey in others.No one here has made it yet

Knowing it

Where to buy: Japanese (katakuriko) and central European grocers.
Worth knowing: Stir it into sauces off the heat, then bring back just to the boil; overcooking thins it.

Kitchens that keep it in

Fujian province, south-eastern ChinaFujianThe cooking of China's south-eastern coast: clear soups, seafood, the sweet-sour red of fermented rice lees, and the street food the Hokkien carried across Asia.9 classics