Optional thick, aged balsamic vinegar or regular balsamic vinegar, reduced to a syrup, for serving
Preheat the oven to 425°F.
Remove the giblets from the chicken, pat dry with paper towels, and place on a rack in a roasting pan.
Cut the onion into about 4 chunks and place inside the cavity of the chicken.
Combine the balsamic vinegar, olive oil, rosemary, oregano, salt, and pepper.
Use your fingers to separate the skin from the breast and pour some of the vinegar mixture under the skin. Pour the remaining mixture inside the cavity and rub some over the outside of the skin.
Put the chicken in the oven for 30 minutes. Reduce oven to 350°F, and roast for an additional 1 to 2 hours, depending on the size of your chicken, or until the breast meat registers 165°F and the thighs register 180°F on an instant-read thermometer. If the skin is browning to quickly, cover lightly with a tent of aluminum foil.
Let rest for about 10 minutes before carving.
If desired, drizzle with the aged or reduced balsamic vinegar for serving.
Recipe by Cupcakes & Kale Chips at http://cupcakesandkalechips.com/2012/04/02/rosemary-balsamic-roast-chicken-and-a-new-job-for-the-hubby/