In a bowl, combine the diced chicken with the soy sauce, Chinese rice wine, cornstarch, salt, and black pepper. Mix well and let it marinate for at least 20 minutes.
In another bowl, whisk together the soy sauce, Chinese black vinegar, hoisin sauce, sugar, cornstarch, and chicken broth (or water). Set this sauce aside.
Heat the vegetable oil in a large skillet or wok over high heat.
Add the marinated chicken to the hot oil and stir-fry for about 3-4 minutes, or until it's cooked through and slightly browned. Remove the chicken from the pan and set it aside.
In the same pan, add a bit more oil if needed. Add the minced garlic, ginger, and red pepper flakes. Stir-fry for about 30 seconds until fragrant.
Add the diced bell pepper and onion to the pan. Stir-fry for 2-3 minutes until they start to soften. Then, add the dry roasted peanuts and stir-fry for an additional minute.
Return the cooked chicken to the pan and mix everything together.
Pour the sauce mixture over the chicken and vegetables. Stir well to coat everything with the sauce.
Continue to cook for an additional 2-3 minutes, or until the sauce thickens and everything is heated through.