In a small bowl combine balsamic vinegar, soy sauce, garlic, 1 tbsp olive oil, honey and black pepper. Whisk until combined.
Add chicken pieces to a medium bowl and then pour marinade over chicken pieces. Toss until chicken is coated with sauce.
Heat a large skillet on medium heat and add chicken with marinade. Cook for about 10-12 minutes until chicken is cooked through and golden brown and sauce is slightly thickened.
Remove chicken from the pan and set aside.
In the same pan, heat 1 tbsp of olive oil and then add peppers and onions on medium-high heat for about 6-7 minutes. Make sure to use a spatula to deglaze all of the flavors and browned bits from the bottom of the pan! Season peppers and onions with salt and pepper if desired to taste.
Add chicken back to the pan (make sure to add back any sauce that you removed, too!) and toss well. Serve over white rice.
Top with green onions and red pepper flakes if desired!