IN CHINA, in the Provence of Yunnan, there is a splendid steamed chicken dish called Yunnan Cah'i Kuo Chi. It is often made by taking a chicken that has been cut into bite-sized pieces, dried mushrooms, bamboo shoots and scallions and placing them in a specially designed Yunnan steamer pot.

The Yunnan pot is somewhat like a round casserole with a distinct tapering in from mid-side to the base. The most convenient model has an 8-inch diameter at the top rim, is 3 1/4 inches deep and holds about six cups of ingredients. Rising from the center of the inside base is a hollow steam chimney.

When the solid ingredients are placed around this chimney a few cups of broth are added. The top of the steamer is put on and the steamer placed above an ordinary saucepan containing boiling water. The steam from the boiling water rises through the hollow base of the chimney, disperses itself along the inside of the lid, condenses and rains gently onto the floating ingredients below. The cooking time varies from 1 1/2 to 2 hours and you must check from time to time to see that there is still water in the lower saucepan.

The dish can be cooked well in advance and reheated before serving. The chicken is usually presented just with a soy sauce dip and the broth later as a soup course. Yunnan pots are available in stores that carry a broad selection of Oriental cooking equipment and usually retail for about $15.

A group of California craftsmen at the Ironstone Pottery Company has produced an American adaptation of the Yunnan pot that has been sold widely throughout the United States during the past few years. It is made of hand-thrown ironstone pottery that has been completely glazed except for the bottom of the pot and the top rim and lid rim which interface. A soft beigey gray with deep-brown speckles, they come in two-, three-, and five-quart capacities. The three-quart size is 7 1/2 inches high and nine inches in diameter and will hold two chickens, which is normally enough to serve eight people, unless you are eating with my sons.

The central chimney inside the pot is shaped like a candlestick holder with a widely flaring top as opposed to the funnel in the classic Yunnan pot which is shaped like a funnel or cone rising and tapering to a small hole at the top. The ironstone steamer design has the advantage of allowing considerably more steam to disperse throughout the pot than the smaller funnel on the traditional pot.

Never use these steamers directly on a burner or submerged in water. They should be placed on a rack that is two or three inches above the boiling water in the saucepan or on top of a narrow saucepan with the rim of the can acting as the support for the steamer. As with the Yunnan pot, you must replenish the water as needed. They can be used with meat, poultry, fish, vegetables, grain and even fruit. The base saucepan can contain any number of different liquids besides water, including stock, wine and beer.

The increasing popularity of this type of cooking is found in its ability to preserve natural flavors and textures as well as protecting vitamins and minerals.

If you would like to test this cooking method without purchasing a Yunnan pot, you can put the ingredients into a deep uncovered bowl. Place the bowl on a rack in a large pot. Keep the water level in the big pot two inches below the bowl and steam with the big pot cover on. You can also use a tubed baking pan with a heavy pot lid on top and the whole contraption over a saucepan. The tubed plan must have a hollow open tube with its top below the rim of the pan.

A third and rather fascinating type or Oriental steamer casserole is the dry steamer made of an ivory stoneware. This pot is often seen in a five-cup size that is six inches in diameter at the top, 3 1/2 inches deep with a gently domed lid and an easy-grasp nod at the top. This heat-proof vessel is filled with various ingredients similar to those used in the Yunnan pots. The steamer casserole is placed on a rack at the bottom of a deep pot. The pot is filled with water until the steamer casserole sides are about 2/3 covered. The heat is turned on and the contents cooked. Additional boiling water is added as needed. Dry steaming is used for long slow cooking in order to concentrate flavors. Food cooked in this method will retain its texture, yet be tender with flavorful juices. Oriental steamer casseroles retail for about $10.