Experience the rich, savory flavors of a comforting French Onion Chicken Casserole. This dish masterfully combines tender chicken, caramelized onions, and a creamy sauce, topped with crispy cheese, making it a perfect meal for any occasion.
Preheat your oven to 375°F (190°C). Season the chicken breasts with salt and pepper on both sides. In a large skillet over medium-high heat, melt 2 tablespoons of butter. Add the chicken breasts and sear for about 5-7 minutes on each side until golden brown and cooked through. Remove from skillet and set aside.
In the same skillet, add the remaining 2 tablespoons of butter and the sliced onions. Cook over medium heat, stirring frequently, for about 15-20 minutes until soft and caramelized. Add garlic powder and thyme, cooking for an additional 2 minutes.
Sprinkle the flour over the caramelized onions and stir well. Gradually pour in the chicken broth while continuously stirring to prevent lumps. Bring to a simmer and let thicken for about 4-5 minutes. Taste and adjust seasoning.
In a large baking dish, place the seared chicken breasts and pour the onion mixture over them. Sprinkle the grated Gruyère and Parmesan cheeses evenly over the top.
Cover the baking dish with aluminum foil and bake for 20 minutes. Remove the foil and continue baking for an additional 10-15 minutes or until the cheese is bubbly and golden brown.
Let the casserole rest for about 5 minutes then garnish with freshly chopped parsley before serving.
