In a large bowl, combine the chicken thighs with soy sauce, dark soy sauce, oyster sauce, black pepper, and corn starch. Mix thoroughly to ensure each piece is evenly coated, then let the mixture marinate for about 10 minutes.

Heat 4 tablespoons of oil in a non-stick pan over medium heat. Cook the marinated chicken pieces for 5 to 7 minutes, turning occasionally, until golden brown and thoroughly cooked.

Once the chicken is cooked, stir in the white parts of the chopped scallions. Cook these for about 1-2 minutes until they soften.

Add the green parts of the scallions, stirring for an additional 10-20 seconds to add a fresh burst of flavor.

Transfer the scallion chicken to a serving platter, garnishing with any remaining scallions or a sprinkle of black pepper if desired.