In a bowl, combine chicken thighs with soy sauce, dark soy sauce, oyster sauce, black pepper powder, and cornstarch. Mix well and let the chicken marinate for about 10 minutes.

In a non-stick pan, heat a tablespoon of vegetable or sesame oil over medium heat.

Add the marinated chicken to the pan, spreading it out evenly. Cook for about 6-8 minutes, turning once, until fully cooked and golden brown.

Stir in the white parts of the scallions, cooking until softened (about 2 minutes). Then add the green parts and stir for 10-20 seconds.

Plate the scallion chicken and garnish with additional pepper or sliced scallions, if desired. Serve with rice or noodles.