In a medium bowl, mix the soy sauce, rice vinegar, cornstarch, ginger, garlic powder, crushed red pepper, and liquid smoke.
Chop the chicken thighs into small bite-size pieces, no more than 3/4 inch. (Panda express uses very small pieces.) Place the chicken pieces in the marinade.
Allow the chicken to marinate at least 10 minutes, but longer is better. Meanwhile, chop the onions and celery. Grind the pepper on the largest setting. If you use pre-ground fine pepper the taste will be too powerful.
Place a wok (or large skillet) over high heat. Add the oil. Once it's hot, stir fry the onions and celery for about 1 minute. It should be just starting to cook, and still firm. Quickly remove from the wok.
Remove the chicken from the marinade with a skimmer, reserving the marinade for later use. Place the chicken in the hot wok. Stir fry for 2 minutes, stirring.
Whisk the marinade and pour it in the wok. Add the black pepper. Stir as the sauce thickens. If it thickens too much, add 1/4 cup water at a time to loosen the sauce until it's the right consistency. It should be thick enough to coat the chicken, but not gummy. Stir in the onions and celery. Simmer another 1-2 minutes. Serve warm.