Preheat oven to 400°F. In a small bowl mix together the honey and balsamic syrup. Heat for 1 minute in the microwave. Set aside. (See Note 2)
Place thinly sliced onion in a rectangle 9x13" casserole dish that has been sprayed with cooking spray or olive oil. Add the chicken breasts on top of the onions.
Baste chicken with half of the honey balsamic glaze.
Sprinkle the chicken with kosher salt, black pepper and garlic powder.
Add 2-3 slices of fresh Mozzarella cheese on top of each chicken breast.
Bake for 30 minutes, depending on the thickness of your chicken breasts. (See Note 1)
Allow to rest 5 minutes before slicing or serving. When serving, top each chicken breast with sautéed onion slices and fresh chopped parsley. Drizzle remaining honey balsamic glaze on top of each chicken breast. Serve on its own, over steamed rice, pasta of choice, or roasted potatoes.
If chicken breasts are too thick (1 inch or more), slice in half horizontally and pound between sheets of plastic wrap for even thickness. For best results, use an instant read thermometer, the chicken is cooked when it reaches internal temperature of 165°F.
I heat the honey and balsamic syrup sometimes if the honey is too thick and doesn't dissolve when mixing with the balsamic vinegar. This is optional.