Marinate the Chicken : In a bowl, combine the chicken strips with 2 tablespoons of soy sauce and cornstarch. Toss to coat and set aside for 10 minutes to marinate.

Prep the Sauce : In a small bowl, mix the remaining soy sauce, oyster sauce, chicken broth, sesame oil, and black pepper. Stir well and set aside.

Cook the Chicken : Heat 1 tablespoon of vegetable oil in a large skillet or wok over medium-high heat. Add the marinated chicken strips and cook until browned and fully cooked, about 4–5 minutes. Remove from the skillet and set aside.

Sauté the Aromatics : In the same skillet, add the remaining 1 tablespoon of vegetable oil. Sauté the minced garlic and ginger until fragrant, about 30 seconds.

Add the Vegetables : Add the sliced mushrooms, bell peppers, and green onions to the skillet. Stir-fry for 3–4 minutes until the vegetables are tender but still crisp.

Combine Everything : Return the cooked chicken to the skillet. Pour in the prepared sauce and toss everything together. Cook for another 2–3 minutes, allowing the flavors to meld and the sauce to thicken slightly.

Serve and Enjoy : Remove from heat and serve your flavorful chicken and mushroom stir-fry over steamed rice, noodles, or as is. Garnish with additional green onions if desired.