Slice the boneless chicken breasts into thin strips. Clean and slice the mushrooms. Slice the red bell pepper and onion, and chop the garlic cloves.

In a small bowl, combine the chicken strips with black pepper, season salt, and teaspoon cornstarch. Mix well and let it marinate for 10–15 minutes.

Heat 1 tablespoon vegetable oil in a large skillet or wok over medium-high heat. Add the marinated chicken strips and stir-fry for 4–5 minutes, until cooked through and lightly browned. Remove from the skillet and set aside.

In the same skillet, add the remaining vegetable oil. Add the sliced onions and bell peppers. Sautee for 2 to 3 minutes. and mushrooms for another 2 minutes. Add the chopped garlic and sauté for 30 seconds until fragrant. Stir-fry for 3–4 minutes until the vegetables are slightly softened but still crisp.

In another bowl, whisk together the chicken broth, oyster sauce, honey, rice wine vinegar, tablespoon soy sauce, and 1 teaspoon black pepper. Set aside.

Add sauce to same skillet. Return the cooked chicken to the skillet toss everything together, coating the chicken and vegetables evenly.

Add your cornstarch slurry (teaspoon cornstarch + 2 teaspoons water)

Let the mixture cook for another 2–3 minutes, allowing the sauce to thicken slightly and cling to the ingredients.

Transfer the black pepper chicken with mushrooms to a serving dish. Garnish with chopped green onions or sesame seeds if desired. Serve hot with steamed rice or noodles.