French Onion Chicken

French onion chicken is a mix of flavors of French onion soup, but with chicken. This dish features caramelized onions, and a creamy, cheesy sauce.

French Onion Chicken

This is probably one of my most favorite dishes!

The caramelized onions in this dish are so sweet and flavorful. It is worth the time it takes to caramelize them. All my kids love this dish as well as my French onion beef casserole recipe.

Whether you're cooking for your family or entertaining guests, French Onion chicken is sure to be a hit.

Ingredients

Boneless, Skinless Chicken Breasts
You can also use chicken thighs if you prefer a juicier cut, but adjust cooking time accordingly.

Olive Oil
Used for both searing the chicken and in the onion mixture to carmalize the onions.

Onions
Large yellow or sweet onions work best for caramelizing, as they develop a rich, sweet flavor when cooked slowly.

Butter
Real butter is essential for caramelizing the onions.

Sugar
A small amount of sugar is optional but helps to accelerate the caramelization process.

Garlic
If you’re a garlic lover, feel free to add an extra clove or two.

Thyme
If you don't have fresh thyme, dried thyme works well too.

Heavy Cream
Heavy cream is the base for the cheese sauce, providing a rich, velvety texture.

Gruyere Cheese
If you prefer, you can substitute with Swiss cheese, which offers a similar taste.

Parmesan Cheese
Freshly grated Parmesan is recommended for the best taste.

Salt & Pepper
Adjust to taste based on your preferences.

Fresh Thyme Leaves & Parsley (for Garnish)
Optional.

How to Make French Onion Chicken

Preheat your oven to 375°F (190°C).

Season the chicken with salt and pepper on both sides.

In a large oven-safe skillet or pan, heat 1 tablespoon of olive oil over medium-high heat.

Once the oil is hot, add the chicken breasts to the pan, cooking them until they are browned on both sides, which should take about 3-4 minutes per side.

Once browned, remove the chicken from the pan and set it aside for later.

Using the same pan, add the butter and an additional tablespoon of olive oil over medium heat. As the butter melts, add the thinly sliced onions and sugar (if using).

Cook the onions slowly, stirring occasionally, until they become soft and caramelized.

This process should take about 20-25 minutes. The sugar helps speed up the caramelization, giving the onions a deep, rich flavor.

Once the onions are caramelized, stir in the minced garlic, thyme leaves, salt, and pepper, cooking for an additional 2 minutes until the garlic is fragrant.

Remove the pan from the heat and spread the caramelized onion mixture evenly across the bottom.

Place the seared chicken breasts on top of the onion mixture in the pan.

Next, prepare the cheese sauce by heating the heavy cream in a saucepan over medium heat until it's warm but not boiling.

Gradually add the shredded Gruyere and Parmesan cheeses, stirring constantly until the cheeses are fully melted and the sauce is smooth and creamy.

Season the sauce with salt and pepper to taste. Pour the cheese sauce over the chicken and onions in the skillet, making sure that everything is evenly coated.

Transfer the skillet or pan to the preheated oven and bake the casserole for about 20-25 minutes, or until the chicken is cooked through and the cheese sauce is bubbly and golden brown on top.

Once done, remove the casserole from the oven and let it rest for a few minutes before serving.

For an added touch, garnish with fresh thyme leaves or chopped parsley if desired.

Tips

Here are some tips to help you make the best French onion chicken casserole:

Caramelize the Onions Ahead of Time: Caramelizing onions can take a while, so if you’re short on time, consider prepping them a day or two in advance. Store the caramelized onions in an airtight container in the refrigerator until you're ready to assemble the casserole.

Use Pre-Shredded Cheese: While freshly shredded cheese melts better, using pre-shredded Gruyere and Parmesan can save time without sacrificing too much on quality. Just be sure to choose a good brand without added fillers.

Use a Mandoline for Onions: A mandoline slicer can help you achieve evenly thin onion slices quickly, making sure they cook evenly. If you use a mandoline, make sure to use a cutting glove for safety (seriously, I used to think it wasn't necessary, but learned my lesson well. I also have a friend who learned this the hard way.)

Don’t Rush the Onions: The key to the best flavor is taking your time with the onions. Cook them slowly over medium heat to allow their natural sugars to develop and caramelize fully. This is where the rich, sweet flavor comes from.

Let it Rest: After baking, allow the casserole to rest for a few minutes before serving.

Leftovers

If you have leftovers from your French onion chicken casserole, they can be stored safely in the refrigerator for up to 3-4 days.

Allow the casserole to cool completely before transferring it to an airtight container or covering this dish with plastic wrap.

You can reheat them at 350°F in the oven for about 20 minutes, or until warmed through. Or, you can microwave individual portions for 2-3 minutes, depending on your microwave's power.

Ways to Repurpose the Leftovers

If you are wanting to do something a bit different with the leftovers, here's some ideas:

French Onion Chicken Sandwiches: Shred the leftover chicken and mix it with the caramelized onions and cheese sauce. Spoon the mixture onto a toasted baguette or roll and top with a slice of Swiss or Gruyere cheese. Pop it under the broiler for a few minutes until the cheese is melted and bubbly, creating a delicious French onion chicken sandwich.

French Onion Chicken Pasta: Cook some pasta (like penne or rigatoni) and toss it with the leftover chicken, onions, and cheese sauce. If needed, add a splash of chicken broth or cream to loosen the sauce.

French Onion Chicken Quesadillas: Shred the chicken and mix it with the onions and cheese sauce. Spread the mixture over a flour tortilla, top with extra cheese if desired, and fold it in half. Cook the quesadilla in a skillet over medium heat until the tortilla is crispy and the cheese is melted. Slice and serve with a side of sour cream or salsa.

French Onion Chicken Stuffed Peppers: Use the leftover casserole as a filling for bell peppers. Either chop or shred the chicken. Cut the tops off the peppers and remove the seeds, then stuff them with the chicken, onion, and cheese mixture. Top with a bit of extra cheese and bake at 375°F for about 25-30 minutes, or until the peppers are tender and the filling is hot.

What to Serve With It

Here are some things we pair our French onion chicken with. I do recommend serving it over either rice or buttered egg noodles and then pairing it with a couple side dishes:

Rice or Quinoa: Simple rice or quinoa helps absorb the flavors without overpowering the dish.

Buttered Noodles: Simple buttered noodles are perfect for adding the French onion chicken to the top of.

Green Salad: A crisp green salad with a light vinaigrette pairs wonderfully.

Steamed or Roasted Vegetables: Lightly steamed or roasted veggies like broccoli or green beans also go well.

Mashed Potatoes: Creamy mashed potatoes soak up the delicious cheese sauce.

Crusty Bread: Warm, crusty bread is perfect for sopping up the rich sauce and caramelized onions.