Preheat oven to 425F degrees.
Spray a baking dish with cooking spray.
Pound chicken breasts to an even thickness, but DO NOT pound thin.
Arrange chicken breasts on the bottom of the baking dish.
Add sliced onions over chicken breasts; set aside.
In a mixing bowl, combine honey, soy sauce, rice vinegar, garlic and ginger; whisk until thoroughly combined.
Pour the sauce mixture over the previously prepared chicken; make sure that the chicken is nestled down in the sauce.
Bake for 30 minutes, or until internal temperature of chicken reaches 165F degrees.
Remove from oven and transfer chicken and cooked onions to a serving plate. Set aside.
Transfer the remaining teriyaki sauce from the baking dish to a frying pan or a saucepan set over medium-high heat.
In a separate bowl, whisk together the cold water and cornstarch until the cornstarch is completely dissolved.
Pour the cornstarch mixture into the saucepan over the teriyaki sauce and whisk to combine.
Bring the mixture to a boil and let boil for about 1 to 2 minutes, or until thickened.
Remove from heat and spoon the sauce over the chicken.
Garnish with sesame seeds and chopped green onions.
Serve over rice.