Heat 1 tablespoon of vegetable oil in a large pan over medium-high heat.

Add the chicken pieces and stir-fry until slightly browned and cooked through, about 5-7 minutes. Remove the chicken from the pan and set aside.

In the same pan, add the remaining oil, followed by the sliced onions and bell pepper. Stir-fry for 3-4 minutes until they begin to soften.

Incorporate the minced garlic and sauté for an additional minute until fragrant.

Return the cooked chicken to the pan and mix it in with the vegetables.

In a small bowl, combine soy sauce, oyster sauce, fish sauce, sugar, black pepper, and chicken broth or water, then pour over the chicken and veggies. Stir until well coated and cook for 2-3 minutes.

Toss in chopped green onions and stir for another minute. Taste and adjust seasoning with salt if necessary.