In a mixing bowl, whisk together soy sauce, oyster sauce, sesame oil, and black pepper. Cut the chicken thighs into bite-sized pieces and coat them in the marinade. Let marinate for about 10 minutes.

In a separate small bowl, mix cornstarch with water to create a slurry. Stir until smooth and set aside.

Heat vegetable oil in a large skillet over medium-high heat. Add the marinated chicken in a single layer and sauté for 3-4 minutes until golden brown and cooked through. Remove from the pan.

In the same skillet, add minced garlic and grated ginger. Sauté for about 30 seconds until fragrant.

Add chopped green cabbage and sliced carrots to the skillet. Stir-fry for 3-4 minutes until vegetables are tender yet crisp.

Return the cooked chicken to the skillet. Pour in the reserved marinade and stir well to combine.

Add the cornstarch slurry into the skillet, stirring constantly as the sauce thickens. Cook for an additional 1-2 minutes until the sauce is glossy.

Remove from heat and transfer stir-fry to a serving platter. Garnish with sliced green onions and sesame seeds. Serve hot over jasmine rice or noodles.