In a large bowl, combine chicken thighs with soy sauce, dark soy sauce, oyster sauce, black pepper, and corn starch. Mix well and let marinate for 10 minutes.

Heat 2 tablespoons of oil in a non-stick pan over medium heat. Add the marinated chicken and fry for 5-7 minutes until golden brown and fully cooked.

Add the white parts of the chopped scallions and stir-fry for 1-2 minutes. Then add the green parts of the scallions and stir for another 10-20 seconds.

Remove from heat and serve on a platter. Optionally sprinkle with more black pepper or sliced scallions.