One Skillet Peach Chicken

Name: One Skillet Peach Chicken
Prep time: 5 min
Cook time: 30 min
Total time: 35 min
Cuisine: American, Southern
Ingredients: 1 lb. boneless, skinless chicken thighs; 1 ½ tablespoons vegetable oil, (divided); ¼ cup finely chopped sweet onion; ½ teaspoon minced fresh rosemary; ⅓ cup brown sugar; 2 tablespoons apple cider vinegar; 2 teaspoons Dijon mustard; ½ teaspoon kosher salt, (divided); 3 medium ripe peaches, pitted and chopped (peeling is optional) ((about 2 cups total)); ¼ teaspoon ground black pepper; Optional garnish: additional chopped fresh rosemary or other fresh herbs, such as parsley, thyme, or basil