Mix the sliced chicken with cornstarch, salt, and ½ teaspoon of black pepper until each piece is evenly coated.

Heat 1 tablespoon of oil in a large skillet over medium-high heat. Add the chicken and stir-fry for about 4-5 minutes or until it's browned. Remove from the skillet and set aside.

In the same skillet, add the remaining tablespoon of oil. Stir-fry the sliced onion and bell pepper for 2-3 minutes until they begin to soften.

Add the sliced mushrooms and minced garlic. Cook for an additional 2-3 minutes.

In a small bowl, whisk together the soy sauce, oyster sauce, honey, rice vinegar, and the remaining teaspoon of black pepper.

Pour the sauce over the vegetables, return the cooked chicken to the skillet, and toss together until well-coated and heated through, about 1-2 minutes.

Garnish with chopped green onions and serve hot over rice or noodles.