french onion grilled cheese cut in half and arranged on a white plate

French Onion Grilled Cheese

Reminiscent of a classic diner grilled cheese, but with the added robust flavors of French onion soup!

Who doesn’t love a classic grilled cheese sandwich? There is something so satisfying about melted cheese and bread – it’s my go-to on rainy days. But because it’s a very rich sandwich, it needs some acidity (it’s the reason grilled cheese is often served with tomato soup!). The sweetness and acidity of tomatoes help cut the richness of the sandwich, and complement it beautifully.

What is a French Onion Grilled Cheese?

One of my favorite ways to make delicious grilled cheese is by adding caramelized onions and turning it into a French onion grilled cheese (very similar to a British cheese and onion toastie)! It’s the best of both worlds: French onion soup AND grilled cheese. This way, you don’t have to choose one over the other for dinner.

The caramelized onions are sweet, and a lovely tanginess is provided by the white wine vinegar, which helps to cut the richness of the nutty Gruyère and creamy Swiss cheese. The aromatics from thyme and garlic round out the French onion flavor, and you get this ooey-gooey, toasted sandwich where every bite is perfection. I hope this becomes a favorite grilled cheese recipe in your household!

french onion filling in a silver frying pan

Ingredients

  • Unsalted butter
  • Yellow onion
  • Fresh thyme
  • Garlic
  • White wine vinegar
  • Gruyère cheese
  • Swiss cheese
  • Sourdough bread
french onion cheese and onion toastie in a silver frying pan

Step-By-Step Instructions

  • Over medium heat, melt 2 tablespoons of butter in a large frying pan. Add diced onion and adjust heat to medium-low. Cook until onion is soft and brown, around 30 minutes, stirring every once in a while.
  • Add thyme, garlic, salt, and white wine vinegar, and cook for an additional 2 minutes. Transfer onions to a bowl.
  • Using same skillet, adjust heat to low and add remaining 2 tablespoons of butter to pan. Place two slices of sourdough in pan, and distribute cheese evenly over both slices of sourdough. Add onion mixture and place remaining 2 slices of sourdough on top.
  • Cook on one side until golden brown, 3-4 minutes, then flip and cook other side for another 2 minutes. Remove from pan and cut in half. Serve immediately.
french onion grilled cheese (cheese and onion toastie) cut in half and arranged on a white plate

FAQS

  • Can I substitute a different type of vinegar if I don’t have white wine vinegar on hand? Yes, substitutes such as apple cider vinegar, red wine vinegar, or balsamic vinegar will all work.
  • Is cooking the onions for 30 minutes necessary? Yes. In order to properly caramelize the onions, they need to cook low and slow.
  • Can I use a different type of cheese? Since French onion soup is classically made with Swiss cheese and/or Gruyère, I wouldn’t recommend using a different type of cheese. That said, all cheese is delicious so any substitution will still be tasty!
  • Can I use white or whole wheat bread in place of sourdough? Feel free to use whatever type of bread you have on hand. I prefer sourdough because of its slight tanginess.

More Spring Recipes That You Will Love!

Enjoy your week, and feel free to drop me a line in the comments – I would love to hear if you try this recipe! Or tag me on Instagram @maryannehoekstra to let me know how it turned out! Also, if you are enjoying my blog, please consider recommending it to your friends. They can subscribe here.

french onion grilled cheese cut in half and arranged on a white plate

French Onion Grilled Cheese

Reminiscent of a classic diner grilled cheese, but with the added robust flavors of French onion soup!
4.93 from 13 votes
Prep Time 5 mins
Cook Time 35 mins
Course Main Course
Cuisine American, French
Servings 2 sandwiches

Ingredients
  

  • 4 Tablespoons unsalted butter
  • 1 yellow onion, diced
  • 2 sprigs fresh thyme
  • 1 clove garlic, minced
  • 1/2 teaspoon salt
  • 1/4 teaspoon black pepper
  • 1 Tablespoon white wine vinegar
  • 2 oz. Gruyère (about 3 slices)
  • 2 oz. Swiss cheese (about 3 slices)
  • 4 slices sourdough bread

Instructions
 

  • Over medium heat, melt 2 tablespoons butter in a large frying pan. Add diced onion and adjust heat to medium-low. Cook until onion is soft and brown, around 30 minutes, stirring every once in a while.
  • Add thyme, garlic, salt, and white wine vinegar, and cook for an additional 2 minutes. Transfer onions to a bowl.
  • Using same skillet, adjust heat to low and add remaining 2 tablespoons of butter to pan. Place two slices of sourdough in pan, and distribute cheese evenly over both slices of sourdough. Add onion mixture and place remaining 2 slices of sourdough on top.
  • Cook on one side until golden brown, 3-4 minutes, then flip and cook other side for another 2 minutes. Remove from pan and cut in half. Serve immediately.
Keyword french onion, grilled cheese

25 Comments

  1. 5 stars
    oh my gosh. Two of my favourite things. French onion soup and grilled cheese sandwiches. This was so good, will be making this again soon.

  2. 5 stars
    Wow! What an incredible sandwich. Love that you use gruyere and swiss as they go best with the french onions.

  3. 4 stars
    Delicious combination. Love the cheesy sandwich. Looks super yum and tempting.

  4. 5 stars
    WOW!!! Not sure why I haven’t thought of this before, but adding caramelized onions with all the delicious french onion flavors-holy yum! thanks for the great idea

  5. 5 stars
    Whoa, two amazing things in one grilled sandwich – I didn’t think grilled cheese could get much better but this blew my mind!

  6. 5 stars
    Anything involving onion already has my attention, so this French onion grilled cheese just sounds absolutely PERFECT. Great cheese combination too, can’t wait to try this one!!

  7. 5 stars
    This looks so delicious and the seasoning sounds wonderful! Can’t wait to try this one!

  8. 5 stars
    Love love the combo of cheeses and thyme in this sandwich.

  9. 5 stars
    Oh my does this look delicious or what? I need this grilled cheese in my life!

  10. 5 stars
    Wow, this looks so good. Absolutely love that you added thyme to this grilled cheese sandwich.

  11. 5 stars
    This sounds sooooo good!

  12. Barbara J Haner

    5 stars
    This will be my next Sunday brunch menu item! Sounds and looks so good!!

Leave a Comment

Your email address will not be published. Required fields are marked *

Recipe Rating




*