A decadent French Onion Grilled Cheese Sandwich with caramelized onions, melty Gruyere and toasty bread. A cozy vegetarian dinner perfect for the colder months! 
French Onion Grilled Cheese Sandwich with Caramelized onions, melty Gruyere and toasty bread. A cozy vegetarian dinner perfect for the colder months! #grilledcheese #sandwich #frenchonion #grilledcheesesandwich #vegetarianrecipes www.feastingathome.com
Every once in a while I get a hankering for a gooey, melty, toasty grilled cheese sandwich.  They tick all the boxes for me as far as “comfort food” and I often add other things besides cheese to jazz them up- like this one with summer tomatoes and pesto or this one with leftover thanksgiving turkey.  
But winter is here and I’m craving depth, so I caramelized up some onions and added them to the mix. Over the top delicious!

Perhaps it’s not the “healthiest”, but somehow I feel comfort food, on occasion is totally warranted and reasonable. It’s comforting! And sometimes I just need that.

No judgment. Just pure pleasure. Flavorful, nutty Gruyere cheese is melted over onions that are caramelized long and slow, prepared like traditional French Onion Soup.

The process of caramelizing the onions brings out their delicious complexity and sweetness. I prefer to use a wholesome, whole grain bread- homemade if possible, but in a pinch, store-bought french bread works great too. Serve this with a green salad, dressed with a light Dijon vinaigrette and enjoy the luscious flavors and textures.

French Onion Grilled Cheese Sandwich with Caramelized onions, melty Gruyere and toasty bread. A cozy vegetarian dinner perfect for the colder months! #grilledcheese #sandwich #frenchonion #grilledcheesesandwich #vegetarianrecipes www.feastingathome.com
Gruyere was always the cheese that was too expensive and luxurious to buy in my younger years. These days, I splurge on occasion, when I know it will make a real difference. You could substitute another cheese, and even make this vegan with all the good melty vegan cheeses available!
But I prefer Gruyere here – it’s earthy, complex and nutty, with the perfect balance of sweetness and saltiness, pairing perfectly with the caramelized onions.
For the full-flavored experience, splurge a little and try Gruyere. It will rock your world.
For this recipe, make sure to buy Gruyere that is young and softer, rather than aged…which will be hard with visible cracks.
French Onion Grilled Cheese Sandwich with Caramelized onions, melty Gruyere and toasty bread. A cozy vegetarian dinner perfect for the colder months! #grilledcheese #sandwich #frenchonion #grilledcheesesandwich #vegetarianrecipes www.feastingathome.com

The easiest way to caramelize onions is to use your biggest heavy bottom skillet, set a burner to medium-low heat, and let the pungent onions cook long and slow in a little oil or butter.

Stir every once in a while, but feel free to leave them and attend to other things. At this temperature, the moisture releases and the sugars caramelize steadily, never burning but growing ever more golden and delicious.

At the end, add a pinch of salt and pepper and perhaps a splash of balsamic, port, sherry or beef stock if you like, letting it cook-off. This is the essence of French onion soup.

A delicious French Onion Grilled Cheese Sandwich with Caramelized onions, melty Gruyere and toasty bread. Serve with a salad and you have dinner!| www.feastingathome.com
 I like adding whole grain mustard to the insides of the bread for a little bite. Layer the bread with grated Gruyere, then a generous amount of caramelized onions, then more Gruyere, and top with the other slice of bread.
A delicious French Onion Grilled Cheese Sandwich with Caramelized onions, melty Gruyere and toasty bread. Serve with a salad and you have dinner!| www.feastingathome.com

The secret to Perfectly Grilled Cheese Sandwiches

  • Heat oil, butter or a combination of both (my preference)  in a large ovenproof skillet, over medium heat.
  • Toast both sides of the sandwich until perfectly golden brown
  • Place in a 350F oven until the cheese is nice and melty.
Cut in half and serve with a green salad.
French Onion Grilled Cheese Sandwich with Caramelized onions, melty Gruyere and toasty bread. A cozy vegetarian dinner perfect for the colder months! #grilledcheese #sandwich #frenchonion #grilledcheesesandwich #vegetarianrecipes www.feastingathome.com

Hope you love this French Onion Grilled Cheese Sandwich as much as we do!

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French Onion Grilled Cheese Sandwich with Caramelized onions, melty Gruyere and toasty bread. A cozy vegetarian dinner perfect for the colder months! #grilledcheese #sandwich #frenchonion #grilledcheesesandwich #vegetarianrecipes www.feastingathome.com

French Onion Grilled Cheese Sandwich

★★★★★ 5 from 10 reviews
  • Author: Sylvia Fountaine | Feasting at Home Blog
  • Prep Time: 15 mins
  • Cook Time: 45 mins
  • Total Time: 50 mins
  • Yield: 2 1x
  • Category: Sandwich, vegetarian
  • Method: Stovepot
  • Cuisine: Northwest, vegetarian
  • Diet: Vegetarian
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Description

French onion Grilled Cheese Sandwich with caramelized onions and gruyere cheese. Serve with a salad for a delicious vegetarian dinner. Vegan adaptable.

Ingredients

Scale
  • 1 large red, sweet or yellow onion- thinly sliced about 1/8 in thick
  • 1–2 tablespoons  olive oil
  • generous pinch salt
  • pinch fresh cracked pepper
  • 1 tsp fresh thyme (optional)
  • 1/4 cup sherry cooking wine, port, or beef stock (all optional, or sub a splash of balsamic vinegar)
  • 4 slices hearty bread or French Bread
  • 1 tablespoons butter
  • 1 tablespoon olive oil
  • 1 cup grated or sliced Gruyere cheese ( or meltable vegan cheese)
  •  Whole grain Mustard ( optional)

Instructions

  1. In a large heavy bottom skillet, or cast iron pan, heat oil over medium heat. Add onion and saute for 5 minutes, stirring to coat. Turn heat down to medium low. Stir occasionally and continue sauteing for 20 minutes.
  2. Onions will sweat out their moisture, and eventually caramelize into a beautiful deep golden brown. Add a generous pinch of salt, a splash of port, sherry, or stock (optional) and let the liquid cook off. Remove from pan and wipe it out with a paper towel, to use again.  Preheat oven to 350 F
  3. Spread the bread with whole grain mustard (optional). On two slices, divide and layer shredded Gruyere, top with caramelized onions, sprinkle with fresh thyme leaves, then add the rest of the cheese. “Put the lid on” the sandwiches with the other slices of bread and gently press together
  4. Heat butter and olive oil in the same skillet over medium-low heat. Place sandwiches in the pan and toast, carefully flipping when perfectly golden brown and cheese begins to melt.
  5. Place in a warm oven to fully melt the cheese -which will preventing the bread from getting too dark. Cut in half and enjoy.

Nutrition

  • Serving Size: ½ sandwich
  • Calories: 520
  • Sugar: 4.9 g
  • Sodium: 1049.1 mg
  • Fat: 22.5 g
  • Saturated Fat: 9.5 g
  • Carbohydrates: 58.5 g
  • Fiber: 3.5 g
  • Protein: 21.8 g
  • Cholesterol: 43.9 mg

Keywords: grilled cheese sandwich, grown up grilled cheese, French onion grilled cheese sandwich, grilled cheese sandwich recipes

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Hi, I'm Sylvia!

Chef and author of the whole-foods recipe blog, Feasting at Home, Sylvia Fountaine is a former restaurant owner and caterer turned full-time food blogger. She currently lives in the Pacific Northwest and shares seasonal, healthy recipes along with tips and tricks from her home kitchen.

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Comments

  1. Sylvia,
    Did you try balsamic vinegar with the onions? Just curious.
    I tried port and stock, but I’m thinking balsamic may be a good option, too? What do you think?

    ★★★★★

    Reply

  2. I am a super fan of Sylvia. After emergency, life saving surgery this year, I wanted to find new and healthy recipes to protect and nourish my body. Her excellent and easy to prepare recipes have become a mainstay of our family meal planning. Thank you for your continued creativity. Good for you food that is a sheer joy to eat!! We love you!

    Reply

  6. Me and my best friend are vegetarian and our favorite thing to do is grab a bottle of wine and cook dinner together. THESE WERE UNBELIEVABLY GOOD. We used a mixture of sweet yellow and red onion, spicy brown mustard, and a take and bake Italian loaf from Aldi. This was wildly better than I expected it to be (and I had super high hopes). Will be adding this to my personal cookbook to share for generations!

    ★★★★★

    Reply

  8. Amazing!! We’re new vegetarians and experimenting with lots of new recipes and this one is definitely a keeper. Its like french onion soup on a sandwich.

    ★★★★★

    Reply

  9. “The smell alone, of Gruyere melting in your kitchen, is worth the extra expense. And can turn a grumpy husband into a kitten.”

    Care to try switching up the genders and the adjectives and seeing if it still sounds just as cute?!?

    Reply

  10. I wish you would let people know that they can substitute vegan cheeses and it’ll be just as delicious. My favorite vegan cheeses are Violife mature cheddar slices, and Follow Your Heart smoked Gouda and provolone. You must know about the health hazards of dairy? And the cruelty of taking baby calves from mum? Thank you.

    Reply

    1. That is a great point Susan. At the time I made this recipe ( 2013) the vegan cheeses out there were not the best as far as melt-ability. Now they are meltable and tasty!

      Reply

    2. Thanks to Sylvia and her talent, this a wonderful site for food lovers and exchanging feedback on recipes – not a site to promote one’s views. Gruyère is a wonderful choice!

      ★★★★★

      Reply

  12. Ok, I think died and went to heaven. Holy moly this was spectacular. Hubby loved it too and asked if we could have again tomorrow. 😉

    ★★★★★

    Reply

  13. This is hands down my favorite sandwich recipe. I didn’t like grilled cheese until I met this sandwich! It is fabulous.

    Reply

    1. Ahhh, funny! You are lucky–I unfortunately love all grilled cheese sandwiches!! But this one is one of my favs too!! Thanks for sharing!

      Reply

  15. Yum Yum! Might I add a side of home made apple sauce for dipping this marvelous concoction to honor my dear German daddy! Done!

    Reply

  17. You had me at caramelized! Oh, and the Gruyere! I am melting! Thank you for the inspiration, recipe and beautiful photos!

    Reply

  20. Cheese and onion one of my favorite combinations. Melted and caramelised brings on an even better combo. Make me one please.

    Reply

  21. Those onions looks so amazing and sweet and caramelised and so delicious! My mouth is watering haha
    http://youtube.com/addalittlefood

    Reply

  22. This looks so delicious. True, comfort food may not always be the healthiest, but it’s good for your SOUL. And as long as you’re using good ingredients (which you obviously are) the result will always be excellent!

    Reply