Biqi (荸荠) – water chestnut (Eleocharis dulcis) is a grass-like aquatic vegetable. Despite the name (which comes from the shape) biqi isn’t a nut. It's a round corm. In other words it grows underground (or in this case - in the mud). Edible part is a white, crisp flesh hidden beneath paper-like, brown skin. It’s rich in vitamins - especially B6. Interesting feature about water chestnuts is that they remain crisp even after cooking (thanks to unusual structure of their cell walls).
They usually aren’t sold in supermarkets but you can buy them from numerous street vendors in Southern China. It’s also very cheap – around 10 RMB (~1,5$) for a kilogram.
How to eat them? – Watch below.
How do biqi taste?
They have very mild and slightly sweet flavor. It resembles the taste of a pear. It’s just less sweet and crispier.