2 pounds Vidalia onions, sliced
2 pounds boneless, skinless chicken breasts or thighs
2 cups beef broth
1 cup swiss cheese, grated
1/3 cup extra-virgin olive oil, divided
2 tablespoons all-purpose flour
2 teaspoons balsamic vinegar
1/2 teaspoon dried thyme
1/2 teaspoon dried sage
kosher salt and freshly ground pepper, to taste
- Preheat oven to 350º F.
- Heat 2 tablespoons olive oil in a large, oven-proof pan or skillet over medium heat. Season with salt and cook, stirring occasionally, for 15-20 minutes, or until softened and caramelized.
- Add balsamic vinegar and cook for another 3-5 minutes or until darkened, but not burned.
- Remove onions from heat and transfer to a medium bowl.
- Heat remaining olive oil in skillet and raise heat to medium-high.
- Season chicken breasts with salt, pepper, thyme and sage, then place in skillet and sear on both sides until golden brown. Remove chicken from heat and set aside.
- Pour beef broth into skillet and bring mixture to a boil, scraping up stuck bits from the bottom of pan.
- Return heat to medium-low and whisk in flour, stirring until smooth. Cook for 5-7 minutes, or until mixture has thickened. Taste and adjust seasoning, if necessary.
- Return chicken and onions to pan, stir together with beef gravy, then top with grated swiss cheese.
- Transfer skillet to oven and cook until cheese is melted and bubbly, and chicken is cooked through.
- Remove from oven and serve hot. Enjoy!