MARINATE THE CHICKEN: Add the egg, soy sauce, and cornstarch to a large bowl and mix until well combined. Add the chicken pieces and stir to combine. Cover the bowl and refrigerate for 1 hour.
MAKE THE RICE: Add the rice and 1 1/2 cups water to a saucepan and bring to a boil over medium-high heat. Place a lid on the pan and reduce the heat to low. Simmer, WITHOUT REMOVING THE LID, for 10 minutes. Turn off the heat and let the rice sit, WITHOUT REMOVING THE LID, for 15 more minutes.
MAKE THE SAUCE: Stir together all the sauce ingredients in a bowl until well combined and set aside.
Heat 2 TBSP of peanut oil in a wok over medium-high heat and tilt the pan to coat in the oil. When the oil is hot shake any excess marinade from the chicken pieces then add HALF the chicken to the wok in a single layer. Cook the chicken without moving for 2 minutes then flip and cook 2 to 3 more minutes or until browned. Transfer the chicken to a paper towel lined plate and set aside.
Add 2 more TBSP of oil to the wok and cook the remaining chicken pieces the same way.
Wipe the wok clean and heat the remaining 1 TBSP of oil over medium-high heat. Add the bell peppers, garlic, and ginger and cook, stirring often, for about 2 minutes.
Pour in the sauce and stir to combine. Cook, stirring often, until sauce begins to boil.
Add the chicken back into the wok and stir to combine then reduce heat to medium-low. Simmer over medium-low heat, stirring occasionally, until chicken is cooked through, about 5 more minutes.
Taste and season with additional salt & pepper if necessary. Transfer to a large serving bowl and sprinkle with the sliced green onion. Serve with the steamed rice.