Begin by placing the chicken strips in a bowl and adding soy sauce, oyster sauce, cornstarch, and 1 tablespoon of oil. Mix well to ensure all the pieces are evenly coated. Allow the chicken to marinate for 10-15 minutes.

Heat a large frying pan or wok over medium-high heat and add 2 tablespoons of oil. Once the oil is hot and shimmering, add the marinated chicken. Cook for about 15-17 minutes, stirring occasionally until the chicken is golden brown.

In the same pan, toss in the white parts of the chopped green onion and pour in the beaten eggs. Let the eggs sit for about 30 seconds without stirring, allowing them to set a bit. Then, gently scramble until just cooked through.

Once the eggs are scrambled, add in the frozen vegetables to the pan. Stir-fry for 2-3 minutes until the vegetables are heated through and vibrant in color.

Introduce the cold cooked rice to the vegetable and egg mixture. Use a spatula to break up any clumps, ensuring that the rice grains are separate and fluffy. Add the cooked chicken back into the pan along with soy sauce, oyster sauce, white pepper, sugar, and dark soy sauce (if using).

On high heat, stir-fry the ingredients together for about 2-3 minutes until everything is well combined and heated through. Finish by adding the green tops of the green onions, stirring briefly to mix, and serve.