In a medium bowl, stir in the soy sauce, balsamic vinegar, sesame oil, and cornstarch until the cornstarch is dissolved.
Add the chicken and toss to coat. Let stand at room temperature for about 10 minutes.
In another bowl, combine the balsamic vinegar, soy sauce, hoisin sauce, sesame oil, and cornstarch. Stir until the cornstarch is dissolved and set aside.
In a wok or large skillet over medium high heat, add peanut or vegetable oil. Stir in the crushed red pepper flakes. Add in the chopped red and green bell peppers. Cook for about 3 or 4 minutes until they are slightly softened.
Stir in the minced garlic and grated ginger and continue stirring for about 1 minute.
Add the chicken and continue stirring the chicken for about 4 or 5 minutes or until it is no longer pink.
Pour in the sauce and mix to coat the chicken and vegetables. Stir in the peanuts and cook for another 1 to 2 minutes.
Transfer to a serving plate, sprinkle the green onions on top, and serve over white rice.