French Onion Chicken

This oven-baked French Onion Chicken is stuffed with mozzarella cheese and smothered in a French onion sauce. Serve it with a side of mashed potatoes, there is plenty of caramelized onion sauce to go around!

Be sure to serve this with my Smooth and Creamy Homemade Mashed Potatoes and easy Roasted Carrots.

Seasoned chicken breast stopped with melted mozzarella cheese and French Onion Sauce on top of mashed potatoes on a plate with a fork.

French Onion Chicken

There’s no denying the fact that I am quickly becoming quite the connoisseur when it comes to French Onion recipes.

(Just check out the reviews for my French Onion Soup, Smothered Pork Chops, and even French Onion Chicken Casserole!)

This recipe is not a boring chicken recipe. The chicken is stuffed with mozzarella, topped with more mozzarella, and baked in the most amazing French onion sauce.

The onions take a bit of time to fully caramelize, but the flavor of the sauce is so well-worth the time.

Let’s get into what you’ll need, the basic outline on how it’s done, and some FAQ!


See recipe card at the bottom of this post for ingredient quantities and instructions.

  • Boneless/skinless chicken breasts
  • Salt/pepper
  • Italian seasoning
  • Mozzarella Cheese– a block of low moisture mozzarella melts and tastes the best. You can also add Gruyere, Parmesan, and/or Gouda.
  • Yellow Onions
  • Butter
  • Olive Oil
  • Flour -Optional, helps thicken the sauce.
  • Garlic– fresh garlic minced at home adds the best flavor.
  • Dry White Wine– Dry red wine may also be used. Otherwise you can sub chicken broth.
  • Chicken Broth
  • Fresh Thyme

How to Make it

Heat butter and olive oil in a large oven-safe pan. (Or transfer to a casserole dish prior to baking.)

Add the onions, cook over medium-low heat, stirring periodically, until golden brown and fully caramelized. This takes a good 40 minutes. 

2 skillets filled with onions before and after being cooked and caramelized.

Add garlic and cook for 1 minute. Sprinkle with flour, (optional), and heat for 1-2 minutes.

Increase heat to medium-high.

Add white wine and cook for 5 minutes. Use a silicone spatula to scrap any bits from the bottom of the pan and work it into the sauce.

Add chicken broth and fresh thyme. Continue to heat while you prepare the chicken.

Butterfly a chicken breast and place mozzarella on the bottom side of the chicken.

A skillet filled with French Onion Sauce next to a butterflied chicken breast topped with mozzarella cheese.

Fold the chicken breast back over to close it and season with salt, pepper, and Italian seasoning. 

Place the chicken in the oven-safe pan with the French Onion sauce. Top generously with mozzarella cheese and transfer to a 400° oven.

Bake uncovered for 25 minutes. Increase heat to 450° and heat until the top begins to brown, watch it carefully.

Ensure the internal temperature of the chicken has reached 165° prior to serving. 

Spoon the chicken generously with French Onion sauce. Serve over mashed potatoes.

Two skillets filled with french onion chicken topped with mozzarella cheese before and after being baked.

Tips for Perfectly Caramelized Onions

  • Don’t cut the onions too thin. They’ll shrivel down to nothing. 1/4 inch is perfect.
  • Use a madoline slicer to cut the onions quickly and evenly.
  • Coat the onions generously in butter and olive oil. Use a silicone spatula and stir occasionally as they cook.
  • Low and slow: Cook the onions over medium-low heat. This process takes some time but the end result is well worth it.
  • Stir Periodically to prevent the onions from sticking to the bottom. If necessary, drizzle with more olive oil.
  • Use more Onions than you think: Onions made up of over 80% water. They shrink down considerably as they cook.

A skillet with French Onion Chicken smothered in a French Onion sauce and topped with melted mozzarella cheese.


Refrigerate for up to 3 days or freeze for up to 3 months. This makes a great freezer meal.


What to Serve With French Onion Chicken

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Chicken Breasts topped with melted mozzarella and a French Onion Sauce on top of mashed potatoes with green beans in the background.

French Onion Chicken

5 from 2 votes
This oven baked French Onion Chicken recipe has mozzarella-stuffed chicken breasts and the most flavorful French Onion Sauce. Serve this over mashed potatoes, there's plenty of sauce to go around!



  • 4 boneless skinless chicken breasts
  • Salt/Pepper
  • 2 Tablespoons Italian seasoning
  • 8 slices mozzarella cheese, or 2.5 cups shredded

French Onion Sauce

  • 4 Tablespoons butter
  • 1 Tablespoon olive oil
  • 2 extra large yellow onions, sliced 1/4 inch thick. See Notes.
  • 1 Tablespoon flour
  • 2 cloves garlic minced
  • 1/3 cup dry white wine, such as Pinot Gritio
  • 1 ¼ cup chicken broth
  • 1 sprig fresh Thyme


  • Note: Use a 12 or 13 inch oven-safe pan to prepare the sauce, add the chicken, and transfer to the oven. If you don’t have one available to you, transfer the French Onion sauce and uncooked chicken to a casserole dish prior to baking.

French Onion Sauce

  • Melt 4 TBS butter and 1 TBS olive oil over medium-low heat.
  • Add the onions to the pan and toss to coat. They will take a good 40 minutes to sufficiently caramelize. Use a silicone spatula to stir them occasionally as they cook.
  • (Refer to process shots in blog post above for visual of what the finished onion should look like.)
  • Add the garlic and cook for an additional minute.
  • Toss with 1 Tablespoon of flour. Heat and stir for 1-2 minutes.
  • Increase the heat to medium-high.
  • Add the white wine and cook for 5 minutes. Use the same silicone spatula to scrape up any bits left on the bottom of the pan to allow the flavor to work its way into the sauce.
  • Add the chicken broth and fresh thyme. Reduce the heat to medium-low and let it simmer and thicken for about 15 minutes. Meanwhile, prepare the chicken.


  • Preheat the oven to 400 degrees.
  • Butterfly the chicken, don’t slice it all the way through.
  • Optional: If you prefer thinner chicken, place plastic wrap over the chicken and use a meat tenderizer to pound it thinner. This will also allow you to fill it with more mozzarella.
  • Fill with sliced or shredded mozzarella and close to seal shut.
  • Season each side with salt, pepper, and Italian seasoning.
  • Top the chicken generously with mozzarella cheese, it's okay if it goes over the sauce as well. (Use as much cheese as you like!)
  • Place the chicken in the pan with the French Onion sauce. OR carefully transfer the sauce and chicken to a 9 x 13 casserole dish if you don't have an oven safe pan.
  • Bake uncovered for 25 minutes.
  • Increase heat to 450 for a few minutes, until the top begins to brown slightly. Watch it closely during this time.
  • Remove from oven. Ensure the internal temperature of the chicken has reached 165° prior to serving.
  • Spoon the top of the chicken generously with French Onion Sauce. Serve with mashed potatoes and vegetables and enjoy!


Onions: I use 2 extra large onions, about 13 oz. each. It seems like a lot but they shrink down considerably as they cook and add a ton of flavor to the sauce.

Additional cheese options include Gouda, grated Parmesan, and Gruyere!

If you don't have dry white wine, dry red wine is your next  best option. (Merlot or Pinot Noir). Otherwise, chicken broth may be used.

This chicken freezes very well for future meals! Best if used within 3 months of freezing.

Serving Suggestion: Serve this with my Smooth and Creamy Homemade Mashed Potatoes.


Calories: 541kcal, Carbohydrates: 13g, Protein: 43g, Fat: 34g, Saturated Fat: 18g, Cholesterol: 158mg, Sodium: 946mg, Potassium: 836mg, Fiber: 3g, Sugar: 4g, Vitamin A: 899IU, Vitamin C: 13mg, Calcium: 422mg, Iron: 2mg