Twists on classic French onion soup have been going viral recently and for good reason. We loved the French onion pasta recipe that made its rounds on TikTok. And now, there's a new iteration we can't get enough of. French onion chicken casserole is rich, creamy, and totally indulgent. The recipe earned rave reviews from our tasters. One called it, "the best chicken dish I've had this year." Here's how to make French onion chicken casserole at home.

French Onion Chicken Casserole Ingredients

The ingredient list may seem long, but it's mostly common pantry staples you may already have on hand.

• Onion: Choose sweet onions for this recipe. Our recipe testers found that one large onion yielded 2 1/2 cups when thinly sliced (be sure to slice them very thin for the best texture). For that unmistakable French onion soup flavor, you'll want to caramelize the onions until they are a deep golden brown color.
• Seasonings: This chicken casserole recipe is flavored with fresh garlic, parsley, salt, and pepper.
• Butter: Like the start of so many delicious recipes, we're cooking the onions in butter.
• Flour: All-purpose flour helps thicken the sauce and gives the casserole its decadent, creamy texture.
• Chicken: This is a great place to use shredded rotisserie chicken. You'll need both the light and dark meat from one whole chicken. Our recipe testers found that most chickens yielded about 3 1/2-4 cups of shredded meat.
• Sour Cream: A small container of sour cream gives the dish a tanginess that balances the sweetness of the caramelized onions.
• Broth: Our Test Kitchen recommends using low-sodium chicken broth to help control the salt level of the finished dish. You can also use homemade chicken stock if you have it on hand.
• Peas: Frozen sweet peas give the casserole a much needed bit of freshness and color. There's no need to thaw them before adding them to the dish.
• Cheese: It wouldn't be a twist on French onion soup without a cheesy topping. We're using the same nutty Gruyere cheese that the classic soup recipe calls for.
• Fried Onions: French fried onions aren't just for topping green bean casserole. Sprinkle them on top just before baking to give the finished dish a nice crunch.

How to Make French Onion Chicken Casserole

The full recipe instructions are below, but here's a quick overview.

1. Cook the Onions: After greasing the baking dish and thinly slicing the onions, it's time to cook them slowly in butter until they become caramelized. The key is to only stir them occasionally so the onions have time to soften and allow the sugars to caramelize.
2. Prep the Chicken: While the onions cook, shred your chicken and mix it with the parsley and sour cream.
3. Thicken the Sauce: Sprinkle the onions with flour and cook to remove the raw flour taste. Pour in broth and seasonings and cook until thickened.
4. Assemble the Casserole: Add the peas to the onion mixture. Pour the onion mixture over the chicken mixture and stir to combine. Add to your prepared baking dish.
5. Top and Bake: Sprinkle with cheese and French fried onions and bake until golden brown.

How to Serve French Onion Casserole

We like this French onion chicken casserole served with a crusty baguette and a bright green salad. It's also delicious over pasta, rice, or a baked potato to soak up the creamy sauce. If you're looking to get more veggies into the meal, steam some broccoli, roast some carrots, or sauté some green beans to serve alongside. If you like a little heat, it's great with a few dashes of hot sauce.

How to Store French Onion Casserole

If you have leftovers, store them in an airtight container in the fridge for 3-4 days.

You can make this casserole up to 1 month ahead and freeze it. Leave off the onions and cheese. When you're ready to serve, thaw the casserole completely in the fridge overnight and top with the cheese and onions before baking. You may need to adjust the baking time if the dish is still frozen in the center.