French Onion Grilled Cheese Sandwich | Feasting At Home

× A decadent French Onion Grilled Cheese Sandwich with caramelized onions, melty Gruyere and toasty bread. A cozy vegetarian dinner perfect for the colder months!  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. 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. 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.  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. 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. Hope you love this French Onion Grilled Cheese Sandwich as much as we do! Print Description French onion Grilled Cheese Sandwich with caramelized onions and gruyere cheese. Serve with a salad for a delicious vegetarian dinner. Vegan adaptable. large red, sweet or yellow onion- thinly sliced about in thick – tablespoons  olive oil pinch fresh cracked pepper 1 tsp fresh thyme (optional) slices hearty bread or French Bread 1 tablespoons butter 1 tablespoon olive oil 1 cup grated or sliced Gruyere cheese ( or meltable vegan cheese) Instructions 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. Place in a warm oven to fully melt the cheese -which will preventing the bread from getting too dark. Cut in half and enjoy. Keywords: grilled cheese sandwich, grown up grilled cheese, French onion grilled cheese sandwich, grilled cheese sandwich recipes Reader Interactions Agnes says November 09, 2021 at 6:44 pm 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? MissTizzy says October 24, 2021 at 9:34 am 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! Emilie Johnston says April 22, 2021 at 11:56 am Kevin says February 12, 2021 at 9:26 am Looks like just the thing for my vegetarian wife this Valentines Weekend – THANKS! Kathy Lundy says February 06, 2021 at 10:01 am Was delicious, loved it ‼️ Eva says January 10, 2021 at 7:01 am 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! JezM says October 15, 2020 at 2:42 pm This was delicious! I forgot the thyme but it was fabulous anyway. Jen W says July 12, 2020 at 11:06 am 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. David says April 19, 2020 at 10:00 pm “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?!? Susan says April 13, 2020 at 7:57 pm 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. Agnes says November 09, 2021 at 6:39 pm 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! Cindy watson says February 14, 2020 at 7:55 pm Sheila Miller says September 15, 2019 at 7:58 am 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. 😉 Micaela Graffeo says December 17, 2015 at 11:59 am This is hands down my favorite sandwich recipe. I didn’t like grilled cheese until I met this sandwich! It is fabulous. Kathy Glasgow says November 06, 2015 at 8:02 am This is just the best sandwich – family raved! Anonymous says September 13, 2014 at 5:06 am Yum Yum! Might I add a side of home made apple sauce for dipping this marvelous concoction to honor my dear German daddy! Done! marla {Family Fresh Cooking} says July 23, 2014 at 12:53 pm Love this grilled cheese recipe! Traci | Vanilla And Bean says You had me at caramelized! Oh, and the Gruyere! I am melting! Thank you for the inspiration, recipe and beautiful photos! Agnes says November 09, 2021 at 6:41 pm A bowl of creamy celery soup or celeriac soup or parsnip soup goes great with they sandwich! Azu says Onion soup in a sandwich! Delicious! Hannah Jade says June 20, 2014 at 10:53 am Completely beautiful – I’m battling some serious cravings now! Bibs @ Tasteometer says June 20, 2014 at 10:22 am Cheese and onion one of my favorite combinations. Melted and caramelised brings on an even better combo. Make me one please. Sylvia Fountaine says Millie l Add A Little says Those onions looks so amazing and sweet and caramelised and so delicious! My mouth is watering hahahttp://youtube.com/addalittlefood Mary Frances says 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! Sylvia Fountaine says Katrina @ Warm Vanilla Sugar says Those onions are total perfection. Yum! Agnes says November 09, 2021 at 6:42 pm A bowl of creamy celery soup or celeriac soup or parsnip soup goes great with the sandwich! Hi, I’m Sylvia- PNW Chef & 2018 Saveur Blog Awards Finalist! 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