French Onion Chicken Bake

1. Turn the heat to medium-low, then add the garlic, pepper, and thyme. Sauté until aromatic.
2. Add the balsamic vinegar and beef broth, then stir until well blended. Make sure to scrape the bottom of the skillet to get the browned bits.
3. Simmer everything for 10 minutes or until the onions caramelize.
4. Add 1/3 of the mixture into the prepared baking dish and spread it evenly.
5. Lay the chicken breasts over the onion layer, then season with salt to taste.
6. Scatter the rest of the onions over the chicken.
7. Sprinkle a generous amount of Parmesan and mozzarella cheese on top of the onions.
8. Place the baking dish inside the preheated oven and bake everything for about 30 minutes or until done.
9. Remove from the oven and allow it to rest for a few minutes at room temperature.

Serve warm and enjoy!