# What You Need:
→ Chicken
01 - 4 boneless, skinless chicken breasts
02 - 1 teaspoon kosher salt
03 - 1/2 teaspoon freshly ground black pepper
04 - 1 tablespoon olive oil
→ Onions
05 - 3 large yellow onions, thinly sliced
06 - 2 tablespoons unsalted butter
07 - 1 tablespoon olive oil
08 - 1/2 teaspoon salt
09 - 1 teaspoon sugar
10 - 2 cloves garlic, minced
11 - 1/2 teaspoon dried thyme
12 - 1/4 cup dry white wine, optional
13 - 1/2 cup beef or chicken broth
→ Topping
14 - 1 1/2 cups shredded Gruyere cheese
15 - 2 tablespoons fresh parsley, chopped, optional
# Step-by-Step:
01 - Set oven temperature to 375°F (190°C).
02 - Season chicken breasts with salt and pepper on both sides. Set aside.
03 - In a large ovenproof skillet over medium heat, add 1 tablespoon olive oil. Sear chicken breasts for 2 to 3 minutes per side until lightly golden. Remove chicken and set aside.
04 - In the same skillet, melt butter with 1 tablespoon olive oil. Add sliced onions and 1/2 teaspoon salt. Cook, stirring often, until onions soften and turn golden, approximately 15 to 20 minutes.
05 - Sprinkle sugar over onions and continue to cook, stirring, until deeply caramelized, approximately 10 minutes more.
06 - Add minced garlic and thyme; cook for 1 minute.
07 - Deglaze the pan with white wine if using, scraping up browned bits, then simmer until liquid reduces by half, approximately 2 minutes.
08 - Stir in broth and simmer for 2 minutes more.
09 - Nestle seared chicken breasts into the onion mixture in the skillet. Spoon some onions over the chicken.
10 - Sprinkle shredded Gruyere evenly over the chicken and onions.
11 - Transfer skillet to the oven and bake uncovered for 20 to 25 minutes, or until chicken reaches an internal temperature of 165°F (74°C) and cheese is melted and golden.
12 - Remove from oven and let rest 5 minutes. Garnish with fresh parsley before serving.
