1cupmozzarella or smoked provolone cheese shredded - see notes about cheese
Instructions
In a pan (preferably with a lid) over medium heat add 1 tablespoon olive oil, cook chicken until it is cooked through, about 5-6 minutes per side. Until chicken reaches 165 degrees internal temp.
Remove the chicken and set aside.
In the same pan add 2 tablespoon olive oil, over medium low heat, slowly cook the onions until they begin to brown, this will take about 15-20 minutes.
Stir in the 3 tablespoon water, 3 chopped garlic cloves, 3 tablespoon brown sugar, 3 tablespoon balsamic vinegar, 3 tablespoon worcestershire sauce, and 1 teaspoon salt. Optionally add a little cayenne or red pepper flakes for heat.Simmer for about 5 minutes over medium low heat. It should thicken slightly as it simmers.
Turn the heat to low, scrape the onion mixture to one side of the pan. Add the chicken breasts back to the pan and then top them with the onion mixture. Sprinkle with cheese.
Pop the lid on the pan and let the cheese melt. If you don't have a lid you can tent some foil over the pan. Or if the pan is oven safe you can broil until the cheese is melted.