In a small bowl, whisk together soy sauce, rice vinegar, sugar, sesame oil, and cornstarch. Set aside.
Heat a wok or large skillet over high heat. Add in vegetable oil and let heat for 1 minute. Add in chicken breast chunks and cook in the oil over high heat until chicken is seared on the outside.
Add in bell peppers and sauce. Continue to cook until bell peppers are tender crisp and chicken is cooked through.
Add in peanuts, garlic, ginger, and chilies and cook 1 to 2 minutes more.
Serve hot and garnish with green onion.
