Make the Sauce: In a small bowl, whisk together freshly ground black pepper, rice vinegar, light soy sauce, dark soy sauce, brown sugar, toasted sesame oil, cornstarch, and a splash of water until smooth.

Marinate the Chicken: In a medium bowl, mix the chicken with a portion of the prepared sauce, cornstarch, and a pinch of salt. Allow to marinate for about 10 minutes.

Brown the Chicken: Heat a skillet over medium-high heat with peanut oil. Add the marinated chicken in a single layer and cook for 3–4 minutes until golden brown, then flip and cook for 2–3 minutes until nearly cooked through.

Stir-Fry Vegetables: In the same skillet, add more oil if needed, then sauté minced garlic, ginger, and chopped chili for 30 seconds. Add sliced onions and green bell peppers, stir-fry for 2–3 minutes.

Combine: Pour the remaining sauce into the skillet and bring to a simmer. Add the browned chicken back, tossing everything together for about 2–3 minutes until heated through.

Serve: Carefully remove from heat, stir in more freshly ground black pepper, and serve hot over steamed rice or noodles.