Save This Recipe
We'll email this post to you, so you can come back to it later!
You ever have one of those nights where you’re just staring into your pantry, hoping dinner walks out on its own? That was me last week. I had a loaf of sourdough that was going stale on the counter, a few sad onions rolling around in the bin, and a half-used box of lasagna noodles I’d been avoiding like laundry.
And wouldn’t you know—sometimes necessity makes the best meals. I started playing around, and what came out of my oven was one of the coziest things I’ve made in a long time: French Onion Lasagna.
Now, I’m not claiming this is traditional. Lord knows I’d get a side-eye from a French chef and a headshake from a Nonna. But it’s rich and savory like a good French onion soup, layered like lasagna should be, and has buttery croutons that’ll have you poking around the pan for just one more bite.
Let’s get into it, shall we?
Why You’ll Fall Head Over Heels for This Dish
-
It’s like French onion soup, but you don’t need a spoon.
-
Croutons in lasagna? Trust me. They steal the show.
-
Melty, golden cheese that’ll have you swooning.
-
Fills the house with that smell that makes folks wander into the kitchen asking, “What’s cookin’?”
-
Make-ahead friendly and freezer-happy.
Ingredients — and What to Do If You’re Missing Something
I’m not fancy, and I don’t expect you to be either. Here’s what I used, and how you can wiggle things around if you need to.
For the lasagna part:
-
1 lb lasagna noodles – Cooked al dente. Not floppy.
-
8 oz mozzarella – Shred it fresh if you can. Bagged stuff works, but fresh melts nicer.
-
6 cups sourdough bread, cubed – Don’t toss your stale bread; this is its big moment.
-
1/4 cup olive oil, 1 tsp garlic powder, S&P – To dress up those bread cubes.
For the béchamel (that’s a fancy word for white cheese sauce):
-
1/4 cup butter + 1/4 cup flour – This makes your roux.
-
4 cups whole milk – Whole milk gives you that dreamy texture.
-
2 cups gruyere cheese, shredded – Nutty and rich. If you can’t find it, use fontina or Swiss.
For the onion filling:
-
3 big yellow onions, sliced – The star of the show.
-
3 tbsp butter + 1/4 cup flour – Helps thicken things into a nice gravy.
-
2 tsp fresh thyme – Dried works too, just use half the amount.
-
1 tbsp balsamic + 1 tsp Worcestershire – Gives it that depth.
-
1 quart beef stock – The better the stock, the better the flavor.
Alright, Let’s Cook
This isn’t hard, just a few cozy steps that come together like a dream. Throw on a good playlist, pour a glass of whatever you like, and let’s do this.
1. Make those croutons
Toss your bread cubes with olive oil, garlic, salt, and pepper. Spread them on a sheet tray and bake at 375°F until golden and toasty—about 18 minutes. Don’t walk away; they go from perfect to burnt quick.
2. Cook your noodles
Boil them in salted water. Give ‘em a quick rinse in cold water so they don’t stick. I like to lay them flat on a dish towel so they don’t clump into a sad lasagna blob.
3. Caramelize those onions
This part takes patience, but it’s worth every second. Melt your butter in a big ol’ pan, toss in the onions, and cook them low and slow until they’re golden brown and smell like heaven. Stir now and then—don’t rush this.
Once they’re soft and beautiful, stir in the flour, then add your stock, thyme, balsamic, and Worcestershire. Let it simmer ‘til thick, like gravy. Season with salt and pepper, then set it aside to cool slightly.
4. Make the cheese sauce
Melt your butter, stir in flour, whisk in milk. Bring it to a bubble (gently), then add your cheese. Stir until creamy. If it looks lumpy, an immersion blender is your best friend.
5. Assembly time!
Layer like this:
-
A little onion mixture on the bottom
-
Noodles
-
Onion filling
-
Croutons
-
Cheese sauce
Repeat that two more times. Top with mozzarella and more gruyere. She’s a stunner already.
6. Bake and rest
Into the oven it goes—375°F for about 40 minutes, until bubbly and golden. Let it rest for 10 minutes before slicing. I know it’s hard to wait, but it holds together better.
Want to Tweak It?
-
No meat? Use veggie stock and skip Worcestershire (or grab the vegan kind).
-
Add mushrooms for an earthy flavor.
-
Like heat? A little chili crisp or red pepper flakes goes a long way.
-
No gruyere? Fontina, Emmental, or even sharp white cheddar in a pinch.
Leftovers? You’ll Be Thankful
Wrap it up and it’ll keep in the fridge for 4 days. It reheats beautifully.
-
Oven: Cover with foil, bake at 350°F until warm—about 20 mins.
-
Microwave: Low and slow. Start at 50% power so it doesn’t rubber up.
-
Freezer: Wrap portions individually. Reheat straight from frozen or thaw overnight.
One More Thing Before You Go…
This isn’t a weeknight whip-it-up dish. It’s a Sunday kind of meal. The kind where the house smells like real cooking, your socks are cozy, and dinner feels like a little celebration of making it through the week.
If you make it—and I hope you do—leave a little note and tell me how it went. Did you swap the cheese? Add a little bacon? Forget the croutons and still love it? I wanna hear all of it.
And if you need me, I’ll be in the kitchen caramelizing onions. Again.
Love from my oven to yours,
French Onion Lasagna
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 and freshly cracked black pepper, to taste
- 1/4 cup butter
- 1/4 cup flour
- 4 cups whole milk
- 2 cups gruyere cheese, grated
- 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 and freshly cracked black pepper, to taste
Instructions
- Preheat oven to 375°F and grease a 10x14 lasagna pan or a 9x13-inch baking dish.
- Toss cubed sourdough bread with olive oil and granulated garlic. Spread on a sheet tray, season with salt and pepper, and bake for 16–20 minutes until golden. Set aside.
- Cook lasagna noodles in boiling salted water until al dente. Drain and set in cold water.
- Caramelize sliced onions in 3 tablespoons butter over medium-low heat until golden brown.
- Stir in flour, then add beef stock, thyme, Worcestershire, and balsamic vinegar. Simmer until thickened. Season to taste. Set aside.
- For the béchamel: Melt butter in a saucepan, whisk in flour and toast 30 seconds. Add milk gradually, whisking constantly until thick. Stir in gruyere until melted. Season and blend if needed.
- To assemble: Spread a little onion filling on the bottom of the pan. Layer noodles, 1/3 of onion filling, 1/3 croutons, drizzle béchamel. Repeat 2 more times.
- Top with mozzarella and remaining gruyere cheese.
- Bake uncovered for 35–40 minutes, or until cheese is golden. Let rest 10 minutes before slicing.
Notes