French Onion Grilled Cheese

French Onion Grilled Cheese: Caramelized onions, melted Swiss cheese, thick sliced buttery bread. The best grilled cheese sandwich ever! 

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Yes, yes, YES! FRENCH ONION GRILLED CHEESE. So many yesses for today's post.

A grilled cheese has to be one of my all time favorite comfort foods. Crispy, buttery bread and tons of gooey melted cheese. What's not to love?

Grilled cheese used to be a staple in this household, but these days it's become more of a treat. One simply cannot have butter, bread, and cheese every day for a meal and not go up a clothing size every other month. Saving grilled cheeses for an only-once-in-a-while indulgence makes them that much more delicious when you actually get to have one. And this French onion grilled cheese? Sweet baby Jesus. It's totally worth unbuttoning your pants for.

Sweet onions get cooked down until jammy and caramelized. I made a separate post (and video) about caramelizing onions last year in case you want to learn more about my method. A bit of fresh thyme and a splash of Worcestershire gives them that unmistakable French onion soup flavor. A few drops of Sherry vinegar adds complexity and wakes everything up, but red wine vinegar will work just as well. You'll probably have some leftover onions. Add them to your scrambled eggs and thank me later.

French Onion Grilled Cheese (Video!) - Overflowing with caramelized onions and melty, cheesy goodness! | Coley Cooks

The onions get smeared onto thick slices of bread and then layered with tons of good quality Swiss cheese. I use 3 slices, but you can never go wrong with a little more. If we're going to eat a grilled cheese we may as well make the most of it.

Smear that bread with plenty of salted butter (salted butter will add that much more flavor) and griddle until golden brown and melted. The key is to cook them over super low heat so the bread doesn't burn before the cheese melts. This is something I always struggle with because I am super impatient and have a hard time waiting. Don't be like me. Practice patience and you will be rewarded handsomely. To ensure the cheese melts, I like to splash a little bit of water on to the griddle and then place a bowl over top to encase the steam. This is an old diner trick that will get your cheese to ooey-gooey perfection in no time.

Add this one to the list of must-makes. You will be so glad you did.

French Onion Grilled Cheese (Video!) - Overflowing with caramelized onions and melty, cheesy goodness! | Coley Cooks

One Year Ago: Tzatziki Sauce (Video!) + Salted Caramel Brownies
Two Years Ago: Meyer Lemon + Cardamom Tart

A hand holding half of a grilled cheese sandwich with cheese melting out of it.
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French Onion Grilled Cheese

French Onion Grilled Cheese: Sweet caramelized onions and tons of gooey melted Swiss cheese sandwiched between thick sliced buttery grilled bread. This is the best grilled cheese sandwich ever! 
Prep Time: 15 minutes
Cook Time: 45 minutes
Total Time: 1 hour
Servings: 2 sandwiches
Calories: 509kcal


  • 2 tablespoons salted butter softened, plus more for the bread
  • 2 medium yellow onions thinly sliced
  • water as needed
  • salt and pepper to taste
  • ½ teaspoon fresh thyme leaves roughly chopped
  • 1 teaspoon Worcestershire sauce
  • 1 teaspoon sugar
  • 1 teaspoon sherry vinegar or red wine vinegar
  • 4 thick slices of bread
  • 6 slices Swiss cheese


  1. Melt 2 tablespoons of butter in a large sauté pan over medium heat, then add the onions. Stir, then cover and cook until softened, about 5 minutes. Add a splash of water and scrape up any browned bits on the bottom, then cover and cook down some more. Repeat this process several more times until the onions have started to turn deep brown and caramelized.
  2. Add fresh thyme, Worcestershire sauce, sugar and vinegar, then season with salt and pepper to taste. Continue cooking for 2-3 more minutes, then transfer onions to a bowl.
  3. Spread a layer of onions on each slice of bread. Top two pieces of bread with a folded slice of Swiss cheese. Top with more onions, then another slice of cheese, then more onions, and one more slice of cheese. Place the remaining slices of bread on top and gently press down.
  4. Preheat a large saute pan or griddle to medium-low heat. Spread butter on one side of each sandwich, then carefully place butter-side-down on the pan. Cook until golden brown, about 4 minutes. In the meantime, butter the top-facing side of bread, then flip and cook until golden on the other side. To melt the cheese, splash a little bit of water on the pan, then invert a large bowl over top to cover the sandwiches for one to two minutes. The water will evaporate and create steam, which will allow the cheese to melt.
  5. Transfer the sandwiches to a cutting board and use a serrated knife to slice them in half on a diagonal. Serve immediately.


Calories: 509kcal | Carbohydrates: 40g | Protein: 21g | Fat: 30g | Saturated Fat: 17g | Polyunsaturated Fat: 2g | Monounsaturated Fat: 7g | Trans Fat: 0.5g | Cholesterol: 78mg | Sodium: 493mg | Potassium: 307mg | Fiber: 4g | Sugar: 10g | Vitamin A: 803IU | Vitamin C: 9mg | Calcium: 558mg | Iron: 3mg

A hand holding half a french onion grilled cheese sandwich with cheese stringing out of it. FRENCH ONION GRILLED CHEESE | This grilled cheese is UNREAL! Gooey Melted Cheese and Deeply Caramelized Onions on Buttery Toasted Bread. The best grilled cheese ever! #easy #best #french #onion #grilled #cheesy #recipe #gruyere #buttery #melted |



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  1. 5 stars
    THIS needs to happen, ASAP! My hubby and I just went to dinner and we ordered a french onion dip as appetizer..which basically was caramelized onions, cheese and toasted bread and we were enamored with how amazing it was. Funny, my hubby was like..oh we should make this into a grilled cheese (light bulb moment)...I kid you not, that was last week and now I see this!!

    1. The difference between good French onion soup and mediocre French onion soup is staggering!! But why not just nix the liquid and get to the really good parts?? This grilled cheese is next level, stupid delicious. I used Trader Joe's thick sliced brioche and it's highly recommended! Nice and soft and just a teeny bit sweet. LMK if you make it!!

  2. 5 stars
    Oh, you evil vixen. I can already feel the Pizza burn forming on the roof of my mouth since I know that I won't wait till it cools before I shove it down my face! I can already taste this blend of two of my favorite foods - French Onion soup and gooey grilled cheese. You should be ashamed! NOT!

    1. Those comments and name calling are 100% warranted. I accept full responsibility. This grilled cheese is SO good. If you can get thick sliced brioche, even better.