Add the chicken and the marinade ingredients into a medium-sized bowl. Mix everything together until the strips are all fully coated. Set aside and allow it to marinate for 10 to 15 minutes.
Mix together the sauce ingredients in a small bowl and set them aside.
Heat the oil over medium-high heat in a large non-stick skillet. Add the marinated chicken into the heated pan. Separate any pieces that may be stuck together. Cook until the bottom turns brown and flip the chicken. Add half of the julienned ginger to the pan and fry it with the chicken, until the bottom of the chicken is browned.
Add the sauce to the pan and stir for about 30 seconds so that the sauce thickens slightly.
Add the rest of the ginger, bell pepper, and chili pepper (if using). Saute and stir briefly to coat everything, about 30 seconds.
Serve hot over steamed rice or boiled noodles as a main dish.