French Onion Grilled Cheese Sandwich (2024)

Just when I thought sandwiches couldn't get any better...this French onion grilled cheese worked its way into my life. And stomach.

Most versions have cheese on the inside, but I went ahead and included cheese on the inside AND on the outside. That way, you get the look and feel of the traditional soup but in sandwich form! After all, more cheese is always better right?

This isn't a traditional recipe in many ways...of course a sandwich isn't going to taste exactly like soup...but it's reminiscent of the best parts of French onion soup (in my opinion). That is: the onions and the cheese!)

By the way, you CAN jump right to the recipe using the button below, but this French onion grilled cheese is a bit unique. If you've got the time, I highly recommend reading through my notes for making it just right!

Jump to Recipe

If you think about it, French onion soup is practically a bowl of onion gravy topped with grilled cheese. So, it seems like a completely natural choice to create a French onion grilled cheese sandwich.

I've been on a French onion kick lately (did you catch my vegetarian French onion soup recipe last month?)

My caramelized onion recipe includes a pinch of cinnamon. It's a special touch that just completely elevates the dish. Cinnamon really complements all of the dish–trust me!

While it does take a bit of extra time and work than a traditional grilled cheese sandwich, I ASSURE you, it's worth every minute. It's even worth the onion tears I cry every time I make it.

What makes this French onion sandwich so special?

White cheddar (or Swiss) inside, and gruyere (or fontina and parmesan) melted ON TOP of the bread after cooking the sandwich

You don't flip these sandwiches–you'll cook one side in the skillet, then move the skillet to the oven. You'll broil the sandwiches for a minute or two until the top piece is golden brown. Then you'll remove the sandwiches, add the cheese and top, and broil them again for a few minutes just like you would with French onion soup.

You can play around with ingredient amounts. The right amount of butter, etc. varies so much depending on the size of your bread. So consider my amounts guidelines!

Heads up...this is a great recipe that uses a cast iron skillet if you have one! If you don't this is the cast iron skillet I have (and love).

The good thing about using a skillet for this sandwich is that you can cook the onions in the same pan and then put your grilled cheese sandwich in the oven without having to switch pans. Any time I can create fewer dirty dishes, I go for it!

French Onion Soup Grilled Cheese Ingredients

Here's what you'll need to create this special grilled cheese sandwich for yourself.

For the caramelized onions

Yellow onions
Olive oil
Butter
Sugar
Black pepper
Cinnamon
Salt
Garlic
Red wine (just a bit for deglazing)

For the French onion grilled cheese sandwich

Large slices of fresh sourdough bread (not just any bread will do for a gourmet grilled cheese like this!)
Butter
Dried thyme and dried rosemary (if you use fresh, you'll just need to use a lot more)
Gruyere cheese to go on top of the sandwich (or a mix of fontina and parmesan if you can't find gruyere)
White cheddar cheese (or Swiss) to go inside the sandwiches

Instructions

Please don't be discouraged if this seems like a lot of steps.

Give it a read-through first, and you'll see it's all pretty simple.

Caramelizing onions

First things first: cut your onions into thin strips. Heat olive oil in a medium or large pan (or ideally, a cast iron skillet) on medium heat. Add the onions, stir well, and let cook for 20 minutes. Stir every few minutes and be very careful the onions don't burn! Turn the heat down if they cook too fast–low and slow is key!
Next, you'll add some butter. Stir well, and continue the cooking and stirring process for another 20 minutes.
Add sugar, salt, cinnamon, and black pepper. Continue cooking for 12 minutes. At the 12 minute mark, add chopped garlic. Cook for another three minutes.
Pour the red wine in the pan (this is deglazing), and use a wooden spoon to scrape any bits off the bottom of the pan. Cook for 2-3 minutes, or until the wine is cooked off. Your onions are done–set them aside.

For the grilled cheese

Melt butter in a microwave-safe dish with dried rosemary and thyme (both or either).
Brush the butter onto one side of each piece of bread. Place two of the buttered slices butter-side-down into the cast iron skillet.
Top the bread with the caramelized onions, then the white cheddar.
Top the cheese and onions with the other slices of bread, butter side up.
Place the skillet on medium heat, and cook for about 5-minutes, or until the bottom of each sandwich is golden and toasty.
While the sandwiches cook, turn your oven to broil.
Once the bottom half of the bread is toasted in the pan, it's time to move your cast-iron skillet to the oven.

(If you don't have a cast-iron skillet, you can use a regular pan to cook the first half. Then, move the French onion sandwiches out of the pan and onto a baking sheet to go into the oven).

Let the sandwiches broil for a minute or two until the top pieces of bread are nice and toasty. (We cook it this way because it's very messy to flip these grilled cheese sandwiches because of all of their fillings!)
Then, remove the skillet or sheet from the oven, and sprinkle the gruyere on top of each sandwich. Return to oven, and let cook for another minute or two, or until the cheese is golden and bubbly.
Remove from the oven and cut in half (careful–it will be extra hot!) Sprinkle with more rosemary and thyme (if you want!) and serve hot!

French Onion Grilled Cheese

📖 Recipe

French Onion Grilled Cheese Sandwich

Chelsea Kram – XO&So: Vegetarian Comfort Food

You've never had a gourmet sandwich quite like this one. Inside, you'll find caramelized onions and white cheddar, then the very top of the sandwich gets a layer of bubbly, melted gruyere. The final result? A French onion grilled cheese that will change the way you think about sandwiches.

Equipment

Cast-iron skillet If you don't have a cast iron skillet, you'll need another oven-safe pan to cook the grilled cheese in the oven. Since this one is too messy to flip, you need to finish cooking it in the oven to get both sides nice and toasty.

Ingredients

For the Caramelized Onions

1 lb yellow onions about two large onions, peeled and cut into thin strips
1 tablespoon olive oil
1 tablespoon butter, unsalted
½ teaspoon sugar
¼ teaspoon salt
2 cloves garlic chopped
3 tablespoon dry red wine I use malbec
cinnamon just a pinch!
black pepper

For the Grilled Cheese

4 slices sourdough bread fresh, large slices
4 tablespoon unsalted butter* melted
⅛ teaspoon dried thyme
⅛ teaspoon dried rosemary
7 oz white cheddar**, shredded or 4 slices of white cheddar
3 oz gruyere*** shredded

Instructions

For the Caramelized Onions

Heat the olive oil over medium heat in a large pan or cast iron skillet. When it's hot, add the sliced onions. Cook and stir often with a wooden spoon until the onions start to soften, about 20 minutes.
Add the butter and cook for another 20 minutes, continuing to stir every 2-4 minutes. Keep a close eye on your onions that they don't burn. Reduce heat if necessary.
See Also
Hosta Companion Plants (What To Plant With Hostas)
Add the salt, sugar, cinnamon, and ground black pepper and continue cooking for another 15 minutes (this is when they'll really start to brown).
Once you reach the 12 minute mark, add the chopped garlic.
Pour in the red wine to deglaze the pan. Using your wooden spoon, scrape the bottom and sides of the pan to get at any caramelized bits. Let cook for 2-3 minutes, or until the wine has mostly cooked off.
Set the onions aside.

For the Grilled Cheese

Melt butter 4 tbsp. of butter a microwave-safe dish with a pinch each of rosemary and thyme (both or either).
Brush the melted butter onto one side of each slide of bread.
Place two slices butter-side-down into the pan or cast iron skillet. Top both slices with the caramelized onions.
Add the shredded or sliced white cheddar on top of the onions.
Close the sandwiches using the other slices of bread, butter side up.
Place the skillet on medium heat, and cook for about 5-minutes, or until the bottom is golden and toasty.
While the sandwiches cook, turn your oven to broil.
Once the bottom half of the bread is toasted in the pan, it's time to move your cast-iron skillet to the oven.****
Let the sandwiches broil for a minute or two until the top piece of bread is golden and toasty.*****
Remove the skillet or sheet from the oven, and sprinkle the gruyere on top of the sandwiches.
Return sandwiches to oven, and let cook for another minute or two, or until the cheese is golden and bubbly.
Remove from the oven and cut in half. Sprinkle with more rosemary and thyme and serve hot.

Notes

*You likely won't use all of this butter, but it's better to have a bit left over than not use enough!

**Swiss will work too.

***A mix of fontina and parmesan works well too.

****(If you don't have a cast-iron skillet, you can use a regular pan to cook the first half. Then, move the sandwiches out of the pan and onto a baking sheet or another oven-safe dish to go into the oven).

*****(We cook it this way because it's very messy to flip these grilled cheese sandwiches because of all of their fillings!)

Nutrition

Calories: 1379kcalCarbohydrates: 98gProtein: 55gFat: 85gSaturated Fat: 49gCholesterol: 227mgSodium: 1769mgPotassium: 627mgFiber: 7gSugar: 15gVitamin A: 2282IUVitamin C: 18mgCalcium: 1266mgIron: 6mg

Keyword French onion soup, grilled cheese

Tried this recipe?Let us know how it was!

This French onion edition marks the 11th Grilled Cheese of the Month for 2020! Any guesses what I'll create next month?

Hope you loooove this one!

Hope you're happy and safe, wherever you're reading this from.

XO,

Chelsea

By the way, I have a new page on my site with a bunch of helpful links. It has links to my social profiles, LTK, Amazon Storefront, etc. There's NO pressure to shop from any of these links. But if you're curious about the products I use, etc., that's where you'll find them. As always, I appreciate your support SO much!