If breasts are very thick, use a sharp knife to slice through the pieces horizontally to make them thinner.
Place chicken breasts in a gallon size Ziploc bag. Add remaining ingredients, seal the bag, and shake to combine.
Place in refrigerator to marinate for at least 30 minutes. (If only marinating for 30 minutes, you can marinate at room temperature — this will help the chicken cook more evenly.)
Heat a large, heavy bottomed skillet over medium heat. Add the chicken breasts and sear the first side for 2-3 minutes. You'll know that the chicken is ready to flip using tongs when the chicken breasts pull away from the pan easily and without sticking.
After you flip to the second side, pour the marinade over the chicken, cover the pan with a lid, and continue cooking for another 5-6 minutes.
Remove lid and use an instant read meat thermometer to check the internal temperature at the thickest portion of the meat. Chicken is finished cooking when the internal temperature reaches 165℉.
If desired, use the tongs to move the chicken around the pan to get some extra balsamic reduction on it.Transfer chicken to a serving platter and let it rest for about 5 minutes, then serve.
Notes
It's crucial to use a pan that is safe for use with oil, since this marinade is oil based.If you don't have a lid for your pan, you could cover it with foil, or finish cooking in the oven at 350°F.You can also make this recipe with bone-in chicken, but the cooking time will be longer.