You’ll love this recipe if you like Chicken Tater Tot Casserole and Chicken Cordon Bleu Casserole.
This casserole takes all the best parts of classic French onion soup and puts them into a bubbly, golden bake that your family will actually get excited about. It’s the kind of dinner you’ll look forward to making because you already know it’ll turn out great — rich, cheesy, and impossible to resist. Serve it once, and you’ll have everyone asking you to make it again.
You don’t have to overthink sides for this casserole — it pairs perfectly with basics like egg noodles, crusty bread, salad, or a simple veggie. Plus, leftovers reheat beautifully, so tomorrow’s lunch is something you’ll genuinely anticipate. Basically, this is your new go-to when you want comfort food that feels impressive without extra effort.
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💛 Why you’ll love this recipe
- Uses simple, budget-friendly ingredients you probably have on hand.
- The chicken cooks right in the sauce, so it stays tender and soaks up great flavor.
- You can swap in rotisserie chicken to make it even quicker.
- Leftovers reheat well for quick lunches the next day.
➡️ Ingredients you’ll need
⏲ How to make this French onion chicken casserole recipe
👉 Easy ingredient swaps
- Chicken Breasts: If using shredded rotisserie chicken, reduce baking time to 20-25 minutes, just enough for the casserole to heat through and cheese to melt.
- Cheddar/Mozzarella: Gruyere or Swiss pair well with caramelized onions.
- Sour Cream: Plain Greek yogurt works if you want something lighter.
- Butter: Olive oil can be used for the onions if you prefer.
✨ Variations
- Extra onions: Add an extra half onion for a stronger onion flavor.
- Mushrooms: Cook sliced mushrooms along with the onions.
- Herbs: A pinch of thyme pairs nicely with caramelized onions and chicken.
- Rice bake: Slice the chicken thinner and layer over 3-4 cups cooked rice, then bake as directed for an easy one-pan meal.
〰️ How to serve
- Carbs — Mashed potatoes, rice, or egg noodles.
- Salad — A simple green salad.
- Vegetables — Steamed broccoli, baked zucchini, roasted carrots, or green beans.
💬 FAQs
Can I prepare this casserole ahead of time?
Yes. Assemble the casserole up to the baking step, cover tightly, and refrigerate for 1-2 days. Add about 10 minutes to the first covered bake since it will be cold.
How long do leftovers last?
Leftovers keep in the fridge for 3-4 days in an airtight container. Reheat in microwave until steaming hot, or bake covered at 350°F for about 15-20 minutes until internal temperature reaches 165°F.
Can I freeze this casserole?
This one does not freeze well because of the dairy in the sauce. The texture changes once thawed, so it’s best to keep it refrigerated and eat it within a few days.
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French Onion Chicken Casserole
Ingredients
Onions
- 3 Tablespoons butter
- 2 large yellow onions (or 3 small), thinly sliced
- 2 Tablespoons water, as needed
Chicken
- 1 teaspoon salt
- 1 teaspoon garlic powder
- ½ teaspoon oregano
- ¼ teaspoon pepper
- 1 ½ pounds chicken breasts
Casserole
- 1 cup milk
- 2 Tablespoons cornstarch
- 1 teaspoon Better Than Bouillon chicken base (or 1 bouillon cube or 1 teaspoon bouillon powder)
- ½ teaspoon salt
- ½ teaspoon onion powder
- ½ teaspoon dried parsley
- 1 cup sour cream
- ½ cup cheddar cheese, freshly shredded
- ¾ cup mozzarella cheese, freshly shredded
- 6 ounces French fried onions
Instructions
- Preheat Oven: Preheat oven to 400 °F and grease a 9×13-inch baking dish.
- Caramelize Onions: Melt 3 Tablespoons butter in a skillet over medium-low heat. Add sliced onions and cook for 25-30 minutes, stirring occasionally, until soft and golden. Add a splash of water if they look too dry. Set aside.
- Prep Chicken: Mix the 1 teaspoon salt, 1 teaspoon garlic powder, ½ teaspoon oregano, and ¼ teaspoon pepper. Pat 1 ½ pounds chicken breasts dry and season both sides evenly. Place chicken in prepared baking dish.
- Make Sauce: Whisk 1 cup milk and 2 Tablespoons cornstarch in a saucepan. Set over medium heat and whisk in 1 teaspoon Better Than Bouillon chicken base (or 1 bouillon cube or 1 teaspoon bouillon powder), ½ teaspoon salt, ½ teaspoon onion powder, and ½ teaspoon dried parsley. Bring to a simmer and cook for about a minute, until thickened. Remove from heat, stir in 1 cup sour cream, and let it cool for about 10 minutes.
- Assemble: Spread caramelized onions evenly over chicken breasts. Stir ½ cup cheddar cheese into the sauce (cheese should soften slightly, not fully melt), then evenly pour sauce over onions and chicken. Sprinkle ¾ cup mozzarella cheese evenly on top.
- Bake: Cover with foil and bake for 35-40 minutes. Remove the foil, top with 6 ounces French fried onions and bake uncovered for another 5-8 minutes, or until chicken reaches 165°F.
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