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French Onion Chicken Casserole

This French Onion Chicken Casserole combines the rich, sweet flavor of caramelized onions with tender shredded chicken, creamy sauce, and a golden cracker topping. Gruyère and mozzarella cheeses melt into the filling, creating a bubbly, comforting casserole that’s both hearty and elegant.
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Prep Time 20 minutes
Cook Time 1 hour
Total Time 1 hour 20 minutes
Servings: 8 Servings
Course: Main Course
Ingredients Equipment Method

Ingredients
  

For the Onions
  • 3 Large yellow onions thinly sliced
  • 3 tbsp Unsalted butter
  • 1 tbsp Olive oil
  • 1 tsp Salt
  • ½ tsp Sugar optional, helps with caramelization
  • ½ tsp Black pepper
  • 2 cloves Garlic minced
  • ½ cup Dry white wine or chicken broth
  • 1 tsp Fresh thyme leaves or ½ tsp dried
For the Casserole
  • 3 cups Cooked chicken shredded (rotisserie works great)
  • 1 (10.5 oz) can Cream of chicken soup
  • ½ cup Sour cream
  • ½ cup Mayonnaise
  • 1 cup Shredded Gruyère cheese or Swiss
  • ½ cup Shredded mozzerella
  • 1 cup Crushed butter crackers (like Ritz) or croutons
  • 2 tbsp Unsalted butter melted
  • Fresh parsley for garnish

Equipment

  • Large skillet
  • Wooden spoon
  • Sharp knife & cutting board
  • Mixing bowls
  • 9x13-inch baking dish
  • Measuring cups & spoons

Method
 

  1. Caramelize the Onions
    In a large skillet, heat butter and olive oil over medium-low heat.
    Add the sliced onions, salt, pepper, and sugar. Cook slowly, stirring often, for 25–30 minutes until deeply golden and caramelized.
    Stir in garlic, thyme, and white wine (or broth). Scrape up any browned bits and cook another 3–4 minutes until liquid is mostly absorbed. Remove from heat and set aside.
  2. Prepare the Casserole Mixture
    Preheat oven to 350°F (175°C). Grease a 9x13-inch baking dish.
    In a large mixing bowl, combine shredded chicken, cream of chicken soup, sour cream, mayonnaise, half of the Gruyère, and half of the mozzarella.
    Fold in half of the caramelized onions (reserve the rest for topping). Mix until well combined.
  3. Assemble
    Spread the chicken mixture evenly into the prepared casserole dish.
    Top with the reserved caramelized onions, spreading them evenly.
    Sprinkle the remaining cheeses over the top.
  4. Cracker Topping
    In a small bowl, mix the crushed crackers with the melted butter.
    Sprinkle over the casserole as the final layer.
  5. Bake
    Bake uncovered for 30–35 minutes, until hot and bubbly with a golden topping.
    Let cool 5–10 minutes before serving. Garnish with fresh parsley.