1 cup bourbon whiskey
1/2 cup firmly-packed dark brown sugar
1 cup ketchup
2 tablespoons Worcestershire sauce
1/4 cup cider vinegar
1 tablespoon freshly-squeezed lemon juice
3 cloves garlic, minced
1/2 teaspoon dry mustard
Place chicken breasts, in a single layer, into an ungreased 13x9-inch baking dish.
In a large bowl, combine whiskey, sugar, ketchup, Worcestershire sauce, vinegar, lemon juice, garlic, mustard, salt, and pepper. Pour bourbon marinade over chicken breasts. Cover and marinate at room temperature for 20 minutes or refrigerate to marinate longer (turning meat over several times). Preheat oven to 300 degrees F. Bake chicken, which has been covered with foil for 2 hours. Turn oven to 350 degrees F. and continue to cook for an additional 30 minutes.