French Onion Smothered Chicken with Mushrooms

Ingredients:
For the Chicken:
Four boneless, skinless chicken breasts
Salt to taste
Black pepper to taste
Two tablespoons of olive oil
One tablespoon of unsalted butter

For the Onion and Mushroom Mixture:
Two large onions, thinly sliced
Two cups of mushrooms, sliced (such as cremini or button mushrooms)
Three cloves of garlic, minced
One teaspoon of fresh thyme or one-half teaspoon of dried thyme
One teaspoon of balsamic vinegar
One cup of low-sodium chicken broth
One cup of shredded Gruyère cheese
One tablespoon of fresh parsley, chopped (for garnish)
Preparation Method:
Begin by preparing the chicken breasts. Pat them dry with paper towels to remove any excess moisture, as this will help achieve a nice sear. Season both sides generously with salt and black pepper.