Name: French Onion Lasagna Recipe
Prep time: 30 min
Cook time: 40 min
Total time: 1 h 20 min
Cuisine: French
Ingredients: 1 lb. lasagna noodles, cooked; 8 oz. mozzarella cheese, grated; 6 cups sourdough bread, cubed; 1/4 cup olive oil; 1 teaspoon granulated garlic; Kosher salt, to taste; Freshly cracked black pepper, to taste; 1/4 cup butter; 1/4 cup all-purpose flour; 4 cups whole milk; 2 cups gruyere cheese, grated; Kosher salt, to taste; Freshly cracked black pepper, to taste; 1/4 cup butter; 1/4 cup all-purpose flour; 3 yellow onions, sliced; 3 tablespoons unsalted butter; 2 teaspoons fresh thyme; 1 teaspoon Worcestershire sauce; 1 tablespoon balsamic vinegar; 1 quart good beef stock; Kosher salt, to taste; Freshly cracked black pepper, to taste

Jump to Recipe· 4.9 from 15 reviews

If you love the comfort of lasagna but crave something a little more sophisticated, you’ll adore this French Onion Lasagna Recipe. It’s like the soul-warming flavors of classic French onion soup have met the cheesy, layered goodness of Italian lasagna, and trust me, it’s a match made in culinary heaven. I first tried melding these two dishes together on a chilly evening, and the rich, caramelized onion flavor combined with melty cheeses and crunchy sourdough croutons quickly became a new favorite for family dinners.

This recipe works beautifully when you want a show-stopping meal for guests or a cozy weekend dinner that feels indulgent but is surprisingly approachable. The French Onion Lasagna Recipe balances creamy béchamel, savory onion filling, and crisp noodles so well—you’ll find it’s both hearty and elegant. Plus, it’s perfect for prepping ahead or making when you want to impress without fuss, which is always a win in my kitchen!

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Why This Recipe Works

Layered Flavors: The caramelized onions and beef stock filling bring deep, savory richness that transforms traditional lasagna.
Unique Texture Contrast: Crisp sourdough croutons add a surprising crunch that balances the soft noodles and creamy sauces.
Creamy Béchamel Sauce: A silky cheese-infused béchamel unites the layers flawlessly, making every bite luscious and smooth.
Versatile and Impressive: It’s an elevated yet comforting dish that works for casual dinners or holiday celebrations alike.

A close-up shot of a square slice of lasagna being lifted by a woman’s hand on a metal spatula from a white baking dish, showing multiple layers including a golden and browned top layer of melted cheese with crunchy bread-like crumbs, beneath it a creamy white cheese layer, and a third visible layer of soft pasta with sauce and onions, all sitting on a white marbled surface with a blue and white striped cloth underneath the baking dish, the background softly blurred, photo taken with an iphone --ar 4:5 --v 7

Ingredients & Why They Work

Each ingredient in this French Onion Lasagna Recipe has a purpose, from the deeply caramelized onions to the crunchy bread cubes that mimic a classic soup topping. Picking good-quality cheeses and a sturdy sourdough bread makes a huge difference here, so don’t skimp on those!

Lasagna Noodles: Cooked al dente so they hold up nicely without getting mushy during baking.
Mozzarella Cheese: Melts beautifully and adds that stretchy, gooey texture we all love in lasagna.
Sourdough Bread: Cubed and toasted to croutons, it adds a toasty crunch and a subtle tang inspired by French onion soup.
Olive Oil: Helps crisp the bread cubes and adds a fruity depth without overpowering the onions.
Granulated Garlic: A little punch that pairs perfectly with caramelized onion sweetness.
Butter: Used in both the onion filling and béchamel for richness and smooth flavor.
Flour: To create the roux that thickens both the onion filling and béchamel sauce.
Whole Milk: The creamy base for the béchamel, adding lushness without heaviness.
Gruyere Cheese: Brings nutty, slightly sweet complexity—essential for that French onion soup vibe.
Yellow Onions: Slowly caramelized to develop that signature sweet, deep flavor.
Fresh Thyme: Adds an herbaceous hint, elevating the savory filling.
Worcestershire Sauce & Balsamic Vinegar: Both provide tangy umami boosts to enrich the onion filling.
Beef Stock: Gives the filling that hearty depth, making it taste like classic French onion soup steaming in the layers.
Kosher Salt & Black Pepper: Balanced seasoning for all components to bring everything alive.

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Note: You’ll find the complete list of ingredients, along with their exact measurements, in the printable recipe card at the bottom of this post.

Tweak to Your Taste

I love making this French Onion Lasagna Recipe mine by swapping cheeses depending on what’s on hand or adding a little more fresh thyme to amp up the herb flavor. You can easily tweak it to suit your favorite ingredients or dietary needs without losing the heart of the dish.

Vegetarian Variation: I sometimes use mushroom broth instead of beef stock and add sautéed mushrooms with the onions for an earthy twist that stands up well.
Cheese Swaps: Swiss or fontina work great instead of gruyere, making it easy to customize based on what’s available or your flavor preference.
Gluten-Free Adaptation: Use gluten-free lasagna noodles and substitute the flour in the roux with a gluten-free all-purpose blend, and you’re good to go.
Extra Crunch: I’ve tossed in toasted walnuts with the croutons for a fun nutty surprise that adds more texture.

Step-by-Step: How I Make French Onion Lasagna Recipe

Step 1: Toast the Sourdough Croutons

Start by preheating your oven to 375°F and prepping a sturdy lasagna pan. Toss cubed sourdough bread with olive oil, granulated garlic, salt, and pepper, then spread on a baking sheet. Bake for 16-20 minutes until golden and crisp—these will add a delightful crunch that surprises every bite. I usually keep an eye on them from the 15-minute mark to avoid any scorching.

Step 2: Cook the Lasagna Noodles

While the croutons bake, bring a large pot of salted water to a boil and cook your lasagna noodles according to package instructions until al dente. Once done, drain and rinse with cold water to prevent sticking—this little trick keeps them flexible and less likely to break when layering.

Step 3: Caramelize the Onions & Make the Filling

This part takes patience but is so worth it. Cook sliced yellow onions slowly in butter over medium-low heat until they turn a soft camel color and seriously sweet aroma fills your kitchen—usually 20-25 minutes. Stir in flour to coat the onions, then gradually add beef stock, thyme, balsamic vinegar, and Worcestershire sauce. Let it simmer until thickened like gravy, then season with salt and pepper. I like to taste here and adjust the acidity or saltiness based on my stock’s richness.

Step 4: Prepare the Béchamel Sauce

In a separate pot, melt butter over medium-high heat, then whisk in flour to form a roux, letting it toast for about 30 seconds. Slowly add whole milk while whisking constantly to avoid lumps and bring it to a gentle boil until it thickens enough to coat a spoon. Reduce the heat and stir in grated gruyere cheese until melted and smooth. If you spot any lumps, an immersion blender fixes it in seconds. Season with salt and pepper to taste.

Step 5: Assemble the French Onion Lasagna

Start with a spoonful of the onion filling spread across the bottom of your pan to keep noodles from sticking. Layer your lasagna noodles in a shingled pattern, then evenly spread a third of the onion filling on top. Sprinkle a third of the toasted croutons, then drizzle with béchamel sauce. Repeat this layering twice more until everything is used up. Finish with a generous topping of gruyere cheese for that golden crust.

Step 6: Bake and Rest

Bake your French Onion Lasagna Recipe uncovered at 375°F for 35-40 minutes or until the top is bubbling and beautifully golden brown. Let it cool for at least 10 minutes before slicing—this resting time helps everything settle and makes serving easier. Patience here really pays off because the layers meld perfectly once cooled.

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Pro Tips for Making French Onion Lasagna Recipe

Slow-Caramelize Your Onions: Take your time to cook onions gently on low heat to develop their deep sweet flavor without burning.
Toast the Roux Properly: Toasting the flour-butter mixture briefly prevents that raw flour taste and builds a better sauce base.
Use an Immersion Blender for Smoothness: If your sauces get lumpy, a quick blitz with an immersion blender saves the day and a lot of stress.
Rest Before Serving: Don’t skip the cooling step to let the layers knit together and make slicing clean and effortless.

How to Serve French Onion Lasagna Recipe

A baked dish with six visible layers of soft, light beige pasta sheets alternating with creamy, light brown sauce layers inside a clear glass baking dish on a white marbled texture. The top layer is golden brown with melted cheese and some crispy, darker brown spots. One slice is taken out, showing thick and rich sauce dripping slightly around the edges and inside the empty space. The dish looks warm, creamy, and richly textured. Photo taken with an iphone --ar 4:5 --v 7

Garnishes

I like to finish my French Onion Lasagna with a sprinkle of fresh thyme leaves or a few finely chopped chives for a pop of color and fresh flavor. Sometimes I add a light drizzle of good-quality olive oil or even a grating of fresh black pepper right before serving, which makes it feel extra special and inviting at the table.

Side Dishes

This lasagna pairs wonderfully with a crisp green salad dressed just lightly with lemon and olive oil or a simple arugula salad sprinkled with parmesan. For a heartier meal, roasted root vegetables or garlic green beans add warmth and balance the richness beautifully.

Creative Ways to Present

For special gatherings, I’ve served this French Onion Lasagna Recipe in individual ramekins to make it feel extra cozy and elegant. Another fun idea is to garnish with crispy shallots on top right out of the oven for an added crunch twist—your guests will love the extra detail.

Make Ahead and Storage

Storing Leftovers

I store leftover French Onion Lasagna tightly covered in the fridge for up to 3 days, and it reheats beautifully. I recommend portioning it out into sized containers so you only heat what you need; the flavors deepen overnight, making leftovers even better.

Freezing

This lasagna freezes well—just assemble it fully but don’t bake, then wrap tightly with plastic wrap and foil. When ready, thaw overnight in the fridge and bake as usual, adding a little extra time if needed. It’s perfect for busy weeks or when you want to prep in advance.

Reheating

To reheat, I cover individual slices with foil and warm them in a 350°F oven for about 15-20 minutes until heated through. This way, the béchamel stays creamy and the top retains its lovely golden crust without drying out.

FAQs

Can I use a different type of cheese in the French Onion Lasagna Recipe?

Absolutely! While gruyere is traditional and gives that nutty, rich flavor, you can substitute with Swiss, fontina, or even a mild cheddar. Just pick a cheese that melts smoothly and complements the sweet onions.
Is it necessary to use beef stock in the onion filling?

Beef stock adds authentic depth reminiscent of French onion soup, but you can switch to vegetable or mushroom broth for a vegetarian version. The flavor will be slightly different but still deliciously savory.
Can I make this French Onion Lasagna Recipe gluten-free?

Yes, just swap lasagna noodles for gluten-free ones and use a gluten-free flour blend to make your roux. It requires no other major changes and tastes equally amazing.
How long can I store leftovers?

Leftovers keep well for up to 3 days in the refrigerator if stored in an airtight container. Make sure to reheat thoroughly before enjoying again.

Final Thoughts

This French Onion Lasagna Recipe has become one of my go-to dishes when I want to wow friends or enjoy a comforting meal with a twist. I love how it takes familiar ingredients and flips them into something unexpectedly delicious and elegant. Give it a try—in your kitchen, you’ll create something warm, flavorful, and uniquely yours every time.