This is from my favorite Chinese cookbook, the Key to Chinese Cooking by Irene Kuo (my review). Velveting ensures not only tenderness but also imparts a velvety texture to meat, chicken and seafood. Kuo is the only person I have seen consistently mention that you can velvet in water as well as oil. I usually velvet in water. If you have time to do it,velveting makes an amazing difference in texture.
1 pound boneless, skinless chicken breasts, cut into the size and shape needed for your recipe
1/2 teaspoon salt
1 tablespoon dry sherry
1 large egg white
1 tablespoon cornstarch
1 tablespoon oil
2 cups oil
Put the cut meat into a bowl, add the salt and sherry, and stir. Beat the egg white only until the gel is completely broken -- it should not be frothy, lest the coating to puff and disintegrate upon cooking. Add this to the chicken, sprinkle in the cornstarch, and mix well. Add the tablespoon of oil and stir until smooth. Let the chicken sit in the refrigerator for at least 30 minutes so that the coating has time to adhere to the meat.
Velveting in Oil
Just before velveting the chicken, assemble everything you need: a wok or deep skillet on the stove, a strainer set over a small pot, and a pair of chopsticks, wooden spoon, or spatula. Do not use sharp implements such as a fork for turning the meat in the oil.
Heat a wok or deep skillet over high heat until very hot; then turned to medium, add 2 cups oil, and heat for about 40 seconds until it is very warm, about 275 degrees, or until it foams a cube of bread or piece of scallion very slowly. Give the coated chicken a big stir and scatter in the pieces; quickly but gently stir them to separate them. The oil should cover every piece. Lower the heat immediately if the chicken begins to sizzle; hot oil will make velveted chicken yellow and hard.
When the meat turns white, which takes about 30 to 45 seconds only, immediately pour both oil and chicken into the strainer, reserving the oil. The chicken is now velveted, ready to be stir-fried. When the oil is cool, strain and rebottle it.
Velveting can be done well before the stir-frying. If you are going to use the chicken in an hour or so, do it in oil as above; do not refrigerate the chicken, however, or it will harden. If you do want to refrigerate or freeze velveted chicken, you must use water instead of oil.
Velveting in Water
Bring 1 quart water to a boil, add 1 tablespoon oil to "grease the liquid," and then lower the heat to maintain a very gentle simmer. Scatter in the chicken, stir to separate, and keep stirring gently until the coating turns white. Then immediately pour into the strainer to drain.
As the name "velveting" implies, the coating is white and fluffy and the meat is as soft as velvet. While the oil method gives the meat a firmer texture, the water method produces a softer coating. In either case, the meat is on the verge of being fully cooked, which is the ideal for the process of stir-frying.