Heat the vegetable oil in a large skillet or wok over medium-high heat.
Add the sliced chicken to the skillet and cook for about 5-7 minutes, or until the chicken is browned and cooked through. Remove the chicken from the skillet and set aside.
In the same skillet, add the sliced onion and cook for 2-3 minutes until softened.
Add the minced garlic and ginger, stirring for about 30 seconds until fragrant.
Add the shredded cabbage to the skillet and stir-fry for 4-5 minutes until the cabbage is tender but still crisp.
Return the cooked chicken to the skillet and pour in the soy sauce, oyster sauce, and sesame oil. Stir well to combine and heat through for another 2-3 minutes.
Season with salt and pepper to taste.
Serve hot, garnished with sliced green onions.
Notes
For added crunch, toss in a handful of sliced bell peppers or carrots during the stir-fry.
Substitute tofu for chicken for a vegetarian option, and adjust cooking times accordingly.