Steps
1. Heat 1 tablespoon of olive oil in a large skillet over medium heat.
2. Season the chicken breast with salt and pepper, then add it to the skillet. Cook for 6-8 minutes on each side, or until cooked through. Remove from the skillet and set aside.
3. In the same skillet, add the remaining tablespoon of olive oil. Add the sliced onions and sauté until they become caramelized and golden brown, about 10-12 minutes.
4. Add the sliced mushrooms to the skillet and cook for another 5 minutes, or until they are tender.
5. Pour in the balsamic vinegar and stir well to coat the onions and mushrooms. Cook for an additional 2 minutes.
6. Slice the cooked chicken breast and serve it topped with the caramelized onion and mushroom mixture.
7. Enjoy!