Begin by cutting the chicken thighs into bite-sized pieces. In a mixing bowl, combine the chicken with soy sauce, dark soy sauce, oyster sauce, black pepper, and corn starch. Ensure all pieces are thoroughly coated in the marinade. Let it sit for about 10 minutes.

In a non-stick pan, pour in a tablespoon of oil and heat it over medium-high heat. Add the marinated chicken pieces in a single layer; cook for about 5-7 minutes, flipping occasionally until cooked through.

Once the chicken is golden brown, introduce the white parts of the scallions to the pan. Stir them in and let the flavors meld for 1-2 minutes.

Add the green parts of the scallions and toss everything together for an additional 10-20 seconds. Remove the pan from heat.

Transfer the scallion chicken to a serving platter, and sprinkle with extra black pepper if desired. Serve hot with steamed rice or noodles.