In your pressure cooker pot, add the washed rice and water.
Close and seal the lid and pressure cook, 20 minutes. If cooking on the stovetop, bring the water to a boil, then add the washed rice. Reduce the heat to medium low and cook, until the rice is very tender and can be easily mashed, about 1 hour.
While the rice is cooking, marinate the chicken. In a medium-sized bowl, add the chicken, oyster sauce, cornstarch, chicken stock powder, and 2 tablespoons water. Stir until most of the water has been absorbed.
Add the cooking oil, and stir until completely coated.
Prepare the rest of the ingredients, and set aside until the rice is ready.
When the rice is done, release the pressure completely and open the lid. Turn on the Saute function over low heat, or equivalent.
Add the chopped celery and carrots and cook, stirring occasionally, 4 minutes.
Add the chicken and all the marinade and cook, stirring, 1 minute.
Add the ginger and stir to combine.
Season with the chicken stock powder, salt, sesame oil and white pepper. Adjust seasoning to taste.
Garnish with fried shallots and chopped green onions, if desired. Serve warm.