1. Marinate the Chicken

• In a bowl, combine chicken pieces with soy sauce, cornstarch, sesame oil, and black pepper.
• Mix well and let marinate for at least 10–15 minutes while you prepare the sauce and vegetables.

2. Prepare the Sauce

• In a small bowl, whisk together soy sauce, oyster or mushroom sauce, vinegar, brown sugar, water, and black pepper.
• Set aside for later use.

3. Stir-Fry the Chicken

• Heat oil in a large skillet or wok over medium-high heat.
• Add marinated chicken pieces and cook for 5–7 minutes, stirring occasionally, until golden and cooked through.
• Remove chicken from the pan and set aside.

4. Cook the Vegetables

• In the same pan, add a little more oil if needed.
• Add garlic and ginger, sauté for 30 seconds until fragrant.
• Add onion, bell pepper, and carrots. Stir-fry for 3–4 minutes until vegetables are slightly tender but still crisp.

5. Combine Chicken and Sauce

• Return cooked chicken to the pan and pour in the prepared sauce.
• Toss everything together, ensuring the sauce coats all ingredients evenly.
• Cook for another 2–3 minutes, allowing the sauce to thicken slightly and cling to the chicken.

6. Garnish and Serve

• Turn off heat and garnish with sliced spring onions and sesame seeds.
• Serve hot with steamed rice, noodles, or flatbread.