Steamed foods are cooked by a gentle moist heat which must circulate freely in order to cook the food. It is an excellent method of bringing out subtle flavours and so is particularly appropriate for fish. Bamboo steamers can be used over water in a wok to steam food, but you could use any one of several utensils.
Put about 5 cm (2 in) of water into a wok, then put a metal or wooden rack into the wok. Bring the water to a simmer, and put the food to be steamed on a heatproof plate. Lower the plate on to the rack and cover the wok tightly with a wok lid. Check the water level from time to time and replenish it with hot water as necessary. The water should never make direct contact with the food.