An iconic Fujian dish, this has been elevated to global status and is now a star item in many Chinese and Southeast Asian restaurants overseas. Plump, good-quality oysters should be used, but street food vendors, ever ingenious, will sometimes use the meat of other similar bivalves. The secret of the dish is in the use of water chestnut flour for the batter. Purists will insist on lard or white cooking fat as the cooking medium, but vegetable oil can be used instead, as here. The finished dish should be fully set but with juicy curds of egg, crispy shards of batter and lightly cooked oysters.