I recently discovered the technique of velveting chicken. It's sort of a parcooking method for chicken so that you can then stir-fry it in your favorite recipe without it overcooking and becoming dry. The results are surprisingly good and the technique is pretty simple, always a combination I like.
Whenever you prepare chicken, I recommend brining the chicken first to make it juicy, tender, and tasty. That holds true for chicken for stir-fry. It's not essential to brine, but the results are worth the small investment of effort and time. If you brine and velvet chicken for your next stir-fry, it'll be the difference between, "This chicken is good," and "Wow, how did you make this?!"
1 1/2 pounds of boneless skinless chicken breast, fat and any other "icky" stuff trimmed away, cut into small bites or small strips for stir-frying (brined if desired), rinsed and patted dry
2 egg whites
2 tablespoons cornstarch
2 cups peanut oil
In a bowl large enough to easily hold the chicken, mix the egg white and cornstarch together. Add the chicken to the egg white/cornstarch mixture and coat well. The easiest way to coat well is to use the tools God gave you (your hands). Cover the bowl and place in the fridge for 30 minutes. Remove from the fridge, empty the chicken into a colander, and allow the excess egg/cornstarch mixture to drain off very well.
Heat the oil in a wok or Dutch oven to 275 degrees. Use a candy/frying thermometer to monitor the temperature, and heat the oil slowly as the oil gets to 275 pretty quickly and it's much more time consuming to wait for the oil to cool back down than it is to slowly bring it to temp in the first place.
When oil reaches 275 degrees, drop the chicken pieces in and stir gently to keep them separate and prevent them from sticking to the bottom of the pan. They just need to cook around 30 seconds until they turn very white. The color change will be really obvious and they'll also float up a bit. Remove with a spider and drain in a colander or on paper towels to remove the excess oil.
**You're now ready to cook the chicken in your favorite stir-fry recipe. Please note that after velveting the chicken will not be fully cooked and will not yet be at a safe temperature for consumption.**
One last note: Using 2 cups of peanut oil for a 30-second cooking process might seem wasteful; however, the oil will still be absolutely pristine after velveting the chicken, so after it cools it can be poured into a jar to save for another use.