In a medium bowl, combine the sliced chicken and cornstarch. Toss until the chicken is evenly coated and set aside for about 10 minutes to marinate.

Heat 1 tablespoon of vegetable oil in a large skillet or wok over medium-high heat. Once hot, add the chicken to the skillet in a single layer. Cook for about 4–5 minutes until browned and cooked through, stirring occasionally. Remove the chicken from the skillet and set aside.

In the same skillet, add the remaining tablespoon of oil. Stir-fry the broccoli, bell pepper, and carrot for 3–4 minutes until the vegetables are crisp-tender.

Add the minced garlic and grated ginger to the vegetables, cooking for an additional 30 seconds until fragrant.

Return the cooked chicken to the skillet with the vegetables. Add the oyster sauce, rice vinegar, sesame oil, honey or brown sugar, and red pepper flakes (if using). Stir well to combine all ingredients, cooking for another 2 minutes until everything is heated through.

Taste and season with salt and pepper as needed. Serve immediately over steamed rice or noodles.