Name: french onion casserole Recipe
Prep time: 15 min
Cook time: 1 h
Total time: 1 h 15 min
Cuisine: French
Ingredients: 6 large onions, thinly sliced (about 2.5 pounds); 4 tablespoons unsalted butter; 1 tablespoon olive oil; 2 teaspoons sugar; 4 cups beef broth; 1 cup heavy cream; 1 teaspoon dried thyme; Salt, to taste; Black pepper, to taste; 1 baguette, sliced into 1-inch pieces; 2 cups shredded Gruyère cheese; 1 cup grated Parmesan cheese

Jump to Recipe

If you adore all things rich, hearty, and bursting with deep, savory flavors, then the french onion casserole is about to become your next favorite comfort dish. This casserole transforms sweet, caramelized onions into a luscious, cheesy delight layered with tender bread and bubbling golden Gruyère and Parmesan cheese. It’s the perfect fusion of the classic French onion soup essence baked into a cozy family-style casserole that everyone will be begging for. Once you’ve tried this recipe, you’ll be hooked on the incredible layers of flavor and the warm, inviting aroma filling your kitchen.

french onion casserole Recipe - Recipe Image

Ingredients You’ll Need

Every ingredient in this french onion casserole plays a crucial role in creating layers of flavor and texture, from the sweet caramelized onions to the creamy cheeses. The simplicity of these staples comes together to produce a dish that’s both elegant and comfortingly familiar.

6 large onions: Thinly sliced to caramelize perfectly and provide that tender, sweet onion base.
4 tablespoons unsalted butter: Adds richness and helps golden the onions without overpowering their natural sweetness.
1 tablespoon olive oil: Works with the butter to prevent burning and deepen the flavor of the onions.
2 teaspoons sugar: Enhances the onions’ sweetness for that classic caramelized taste.
4 cups beef broth: Imparts a robust, savory foundation crucial for the casserole’s depth.
1 cup heavy cream: Brings luxurious creaminess and balances the savory notes.
1 teaspoon dried thyme: Adds a subtle earthy herbiness that complements the onions beautifully.
Salt and pepper: Essential seasonings to bring all the flavors together just right.
1 baguette: Sliced into 1-inch pieces to soak up the savory broth and provide delightful texture.
2 cups shredded Gruyère cheese: Melts perfectly with a nutty flavor that’s signature to any onion casserole.
1 cup grated Parmesan cheese: Adds a sharp, salty kick that crisps up irresistibly on top.

How to Make french onion casserole

Step 1: Caramelize the Onions

Begin by melting the butter with the olive oil in a large skillet over medium heat. Add the thinly sliced onions and stir often as they slowly cook down, turning golden and sweet. This process takes about 25 minutes, and patience here is key to unlocking the deep, rich flavor that defines your casserole. In the final 5 minutes, sprinkle the sugar over the onions to boost their caramelization and bring out a beautiful sweetness.

Step 2: Create the Creamy Broth

Once your onions are perfectly caramelized, add the beef broth, heavy cream, dried thyme, salt, and pepper directly to the skillet. Stir everything together and bring the mixture to a simmer. This step melds the flavors, creating a rich, creamy broth that will soak into the bread and meld with the cheese for that signature french onion casserole taste.

Step 3: Build the Casserole Layers

In a mixing bowl or your casserole dish, start by layering half of the baguette slices. These act as sponges to absorb the flavorful broth. Pour half of the onion and broth mixture evenly over the bread, then sprinkle half of the shredded Gruyère and grated Parmesan cheese on top. Repeat this layering process with the remaining bread, onion mixture, and cheeses to create a luscious, multi-layered dish bursting with flavor.

Step 4: Bake to Perfection

Preheat your oven to 350°F (175°C) and place the layered casserole inside. Bake for 30 minutes until the cheese melts thoroughly, turns bubbly, and develops a gorgeous golden brown crust on top. This final cooking step deepens the flavors even further and creates that irresistible texture contrast between creamy onions and crisp cheese topping.

Step 5: Let It Rest and Serve

After baking, allow the casserole to cool for a few minutes before serving. This resting time lets the layers settle and makes scooping easier. Plus, it’s the perfect moment to anticipate each delectable bite of this soul-warming french onion casserole.

How to Serve french onion casserole

Garnishes

A sprinkle of freshly chopped parsley or a few thyme leaves on top can add a pop of color and a fresh herbal note to balance the richness. For extra indulgence, a drizzle of a high-quality olive oil or a touch of cracked black pepper over the golden cheese crust can really elevate the presentation and flavor.

Side Dishes

This french onion casserole is quite hearty on its own, but it pairs beautifully with crisp, refreshing sides like a simple green salad with a lemon vinaigrette or roasted seasonal vegetables. For a fuller meal, roasted chicken or a juicy steak complements the deep onion and cheese flavors perfectly.

Creative Ways to Present

For a festive twist, try serving the casserole in individual ramekins or mini cast iron skillets. This makes for charming, personal-sized portions that look beautiful on any dinner table. Alternatively, top the casserole with caramelized onions and extra cheese for a dramatic layered appearance before baking.

Make Ahead and Storage

Storing Leftovers

Leftover french onion casserole keeps wonderfully in an airtight container in the refrigerator for up to 3 days. The flavors often deepen overnight, making your next serving even more delicious. To retain the best texture, avoid covering the dish while still hot to prevent sogginess.

Freezing

You can freeze the casserole before baking; wrap it tightly in plastic wrap and aluminum foil to protect it from freezer burn. Frozen casseroles are best used within 2 months for optimal taste. Thaw overnight in the fridge before baking, adjusting cooking time as needed.

Reheating

Reheat leftovers in a preheated oven at 325°F (160°C) for about 15–20 minutes until warmed through and bubbly again. Avoid microwaving if possible to preserve the casserole’s texture and to keep the cheese from becoming rubbery.

FAQs

Can I use a different type of cheese?

Absolutely! While Gruyère and Parmesan create the perfect blend of creaminess and sharpness, you can substitute with mozzarella, Swiss, or even fontina for a slightly different but equally delicious result.

Is it possible to make this vegetarian?

Yes, simply replace the beef broth with a rich vegetable broth to keep the casserole flavorful while making it vegetarian-friendly. Adding a splash of soy sauce or Worcestershire sauce (check for vegetarian versions) can deepen the umami taste.

Can I use different bread?

While a baguette is ideal for its texture and absorbency, crusty bread like sourdough or a country loaf can work well too. Just ensure the bread is sturdy enough to hold the broth without becoming mushy.

How long can I prepare this in advance?

You can assemble the casserole a few hours ahead and keep it covered in the fridge. Bake it shortly before serving to ensure fresh, bubbly cheese and beautifully baked layers.

Does the casserole freeze well after baking?

It does, but the texture of the bread may become a bit softer after freezing and reheating. For best texture, freeze before baking and cook from frozen, as suggested.

Final Thoughts

There is something so incredibly satisfying about pulling a hot, bubbling french onion casserole from the oven – the aroma alone invites everyone to gather around the table. This dish is a perfect marriage of simple ingredients with extraordinary flavor, comfort, and indulgence all in one. Whether you’re serving it as a cozy family dinner or bringing it to a potluck, it’s sure to be a crowd-pleaser that becomes a beloved classic in your recipe collection. Give it a try, and prepare to fall in love with every cheesy, onion-packed bite!

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french onion casserole Recipe

★★★★★

4.8 from 20 reviews

Author: Sophie
Total Time: 1 hour 15 minutes
Yield: 6 servings 1x
Diet: Low Salt

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Description

This French Onion Casserole is a comforting dish featuring caramelized onions simmered in a rich beef broth and cream mixture, layered with crusty baguette slices and topped with melted Gruyère and Parmesan cheeses. Baked to golden perfection, it combines savory, sweet, and creamy flavors in a hearty casserole perfect for a cozy meal.

Instructions

Preheat the Oven: Preheat your oven to 350°F (175°C) to prepare it for baking the casserole later.
Caramelize the Onions: In a large skillet, melt the butter with olive oil over medium heat. Add the thinly sliced onions and stir frequently, cooking them for about 25 minutes until they are golden brown and caramelized for deep, sweet flavor.
Add Sugar: In the last 5 minutes of cooking the onions, sprinkle in the sugar. This helps enhance the natural sweetness of the onions, balancing their savory profile.
Simmer with Broth and Cream: Add the beef broth, heavy cream, dried thyme, salt, and pepper to the skillet. Stir to combine, then bring the mixture to a simmer and cook for another 5 minutes to meld all the flavors.
First Layer: In a casserole dish, arrange half of the baguette slices in an even layer. Pour half of the onion and broth mixture over the bread, then evenly sprinkle half of the shredded Gruyère and Parmesan cheeses on top.
Second Layer: Repeat the layering by adding the remaining baguette slices, followed by the rest of the onion mixture and the remaining Gruyère and Parmesan cheeses on top.
Bake the Casserole: Place the assembled casserole in the preheated oven and bake for 30 minutes, or until the cheeses are melted, bubbly, and the top is golden brown.
Cool and Serve: Remove the casserole from the oven and allow it to cool for a few minutes to set before serving warm.

Notes

Use good quality beef broth for the best depth of flavor.
Gruyère cheese melts beautifully and adds a nutty flavor; you can substitute with Swiss cheese if needed.
For a vegetarian version, replace beef broth with vegetable broth.
If you prefer less cream, reduce the heavy cream slightly or substitute with half-and-half.
The casserole is excellent served alongside a green salad or roasted vegetables.

Prep Time: 15 minutes
Cook Time: 60 minutes
Category: Casserole
Method: Baking
Cuisine: French