In parboiling, ingredients are cut and washed first, then put in a large pot in which they can float freely, over high heat. Vegetables to be eaten crisp, like broccoli, are removed from the water just before they come to a full boil; those that cannot be eaten raw or take a long time to cook should remain in the pot for whatever time is required after boiling starts. Slow and prolonged boiling destroys flavor to some degree and certainly much nutritional value is lost in the boiling water that is discarded.
Parboiled ingredients are poured with the water into a colander, rinsed or soaked in cold water until thoroughly cooled, and used as the recipe directs, or in salads. Parboiled vegetables are often used in banquet dishes where time may be limited. For full boiling, as in preparing soups, the Chinese employ a slow simmering process. As soon as the water boils, the heat is turned low and the soup allowed to simmer for whatever period of time is necessary. However, preparing soups by rapid boiling in which intense heat is used will result in the same preservation of color, texture, shape, and nutrition as in tossed cooking.
Boiling could be considered the simplest among all the Chinese cooking methods. It simply involves placing food in boiling water. It is mainly used for cooking small-sized and soft ingredients, especially for most of the vegetable soups like Tomato and Egg Soup and Tofu Soup. Prepared ingredients are placed into a wok, along with water and appropriate seasonings when the surface of the water is continually agitated by large bubbles. Dishes cooked by boiling always taste fresh and clear, for it takes a shorter time than braising.
Strictly speaking, this means cooking food in boiling water (A liquid is boiling when the surface is continually agitated by large bubbles). Violent boiling should be avoided. It wastes fuel; it does not cook the food any faster, it tends to make the food break up and so spoils the appearance; the liquid is evaporated too quickly with the consequent danger of the food burning. There are one or two exceptions to this rule; for example, when one wants to drive off water quickly from syrup or a sauce to make it thicker, then violent boiling with the lid off hastens the process.
In Chinese cooking, there is very little big-fire boiling, as a complete process. Chinese would not consider eating boiled potatoes. After a thing is boiled, the natural question is – Now what of it? Quick plain boiling is often only a preparatory process for other ways of cooking – where the term parboil comes into place. There are some exceptions, such as plain boiled celery cabbage with salt and a little lard, or boiled yam, to eat with sugar. But celery cabbage and yam are such cook-proof things that they are good in any method prepared. It’s not necessary to use continued big fire after water has started to boil, because water cannot be hotter than 100° C or 212°F.
Turn the fire to medium if you want but to make sure that it is at least hot in all parts, especially in a large tall boiling or steaming pot, the fire must be big enough for you to see the steam come out.