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French onion chicken casserole

French Onion Chicken Casserole

This French onion chicken casserole combines juicy baked chicken, deeply caramelized onions, a savory broth-based sauce, and melted Gruyère cheese in one comforting dish. The slow-cooked onions provide the signature sweet and savory French onion flavor, while the cheese creates a rich, golden topping. It's a hearty main-course dinner that's particularly good served with mashed potatoes, crusty bread, roasted vegetables, or a simple green salad.
The cooking approach is consistent with published French onion chicken recipes, which commonly rely on caramelized onions, browned chicken, melted cheese, and an oven finish.
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Prep Time 15 minutes
Cook Time 45 minutes
Total Time 1 hour
Servings: 4 Servings
Course: Main Course
Cuisine: American, French
Calories: 520
Ingredients Method

Ingredients
  

  • 4 boneless-skinless chicken breasts about 6 ounces (170 g) each
  • 2 tablespoons olive oil
  • 3 large yellow onions thinly sliced
  • 2 tablespoons unsalted butter
  • 3 cloves garlic minced
  • 1 cup chicken broth
  • 1 teaspoon Worcestershire sauce
  • 1 teaspoon dried thyme
  • 1 teaspoon salt divided
  • ½ teaspoon black pepper
  • 1 cup shredded Gruyère cheese
  • 2 tablespoons fresh parsley chopped, optional

Method
 

Preheat the oven.
  1. Preheat your oven to 400°F (200°C). Lightly grease a large baking dish.
Prepare the chicken.
  1. Pat the chicken breasts dry with paper towels. If they are particularly thick, gently pound them to an even thickness. Season both sides with ½ teaspoon salt, black pepper, and dried thyme.
Brown the chicken.
  1. Heat the olive oil in a large oven-safe skillet over medium-high heat. Add the chicken and cook for about 3–4 minutes per side, until nicely browned. The chicken does not need to be cooked through yet. Transfer it to a plate.
Caramelize the onions.
  1. Reduce the heat to medium-low and add the butter to the same skillet. Add the sliced onions and the remaining ½ teaspoon salt. Cook for approximately 25–30 minutes, stirring occasionally, until the onions are soft and deeply golden brown. If they begin sticking, add a small splash of the chicken broth and scrape the bottom of the pan.
Add the garlic and sauce.
  1. Stir in the minced garlic and cook for about 1 minute. Pour in the remaining chicken broth and Worcestershire sauce. Stir well, scraping up any browned bits from the bottom of the skillet. Simmer for 3–5 minutes.
Assemble the casserole.
  1. Place the browned chicken breasts in the prepared baking dish. Spoon the caramelized onions and sauce evenly over the chicken.
Add the cheese.
  1. Sprinkle the shredded Gruyère evenly over the chicken and onions.
Bake.
  1. Bake uncovered for approximately 15–20 minutes, or until the chicken reaches an internal temperature of 165°F (74°C) and the cheese is melted and bubbling.
Brown the cheese.
  1. For a more golden topping, switch the oven to broil for 1–2 minutes. Watch it carefully so the cheese doesn't burn.
Rest and serve.
  1. Remove the casserole from the oven and let it rest for 5 minutes. Garnish with fresh parsley if desired, then serve hot.