Marinate the Chicken: In a bowl, combine the chicken pieces with soy sauce, a pinch of salt, and 1 tablespoon of cornstarch. Mix well and let it marinate for at least 15 minutes.
Prepare the Sauce: In a small bowl, mix the remaining cornstarch with chicken broth until smooth. Set aside.
Sear the Chicken: Heat vegetable oil in a large skillet or wok over medium-high heat. Add the marinated chicken and cook until browned and cooked through, about 5-7 minutes. Remove from the skillet and set aside.
Cook the Vegetables: In the same skillet, add a bit more oil if needed. Add the garlic, red, green, and yellow bell peppers, carrot, and broccoli. Stir-fry for about 5-7 minutes until the vegetables are tender-crisp.
Combine and Season: Return the cooked chicken to the skillet. Add the ground black pepper, oyster sauce, and the chicken broth mixture. Stir well to coat everything evenly. Cook for an additional 2-3 minutes until the sauce has thickened.
Garnish and Serve: Remove from heat and garnish with chopped green onions. Serve immediately over cooked rice.
