To prepare the chicken, cut the chicken thighs into small pieces and place them in a mixing bowl. Season with salt first, then mix well. Add the white pepper, soy sauce, and dark soy sauce and mix until combined. In a small bowl, combine the cornstarch and water to make a slurry, then pour it into the chicken and mix well. Finally, add the cooking oil and mix until evenly coated. Let the chicken marinate while preparing the other ingredients.
To prepare the vegetables, cut the cabbage into bite-size pieces and slice the scallions. Mince the garlic and ginger and set everything aside.
To make the stir-fry sauce, in a bowl, combine the tapioca starch and water until smooth. Whisk in the soy sauce, dark soy sauce, oyster sauce, and chicken stock until fully combined.
To stir-fry the chicken, in a wok over high heat, add 1 tablespoon of cooking oil. Add the marinated chicken and spread it out in a single layer. Stir-fry for about 4 minutes until fully cooked through. Add the garlic and ginger and stir-fry for about 10 seconds until fragrant. Remove the chicken from the wok and set aside.
To stir-fry the cabbage, in the same wok over high heat, add the remaining 1 tablespoon of cooking oil. Add the cabbage and stir-fry for about 20 seconds until slightly softened but still crisp.
To combine everything, return the chicken to the wok and pour in the sauce. Stir-fry until the sauce thickens and coats the chicken evenly, creating a glossy finish. Lastly, add the scallions and give everything one final toss before serving.
