This post may contain affiliate links. Learn more.

If you like French onion soup and you like grilled cheese, you’ll love French onion grilled cheese. This recipe takes the savory and gently sweet flavors to the next level. Don’t miss it.

french onion grilled cheese on a plate with a napkin
Want to save this recipe?
Enter your email below and I’ll send it to your inbox. Plus get great new recipes every week!
Please enable JavaScript in your browser to complete this form.

Why we love this recipe

Grilled cheese speaks for itself where comfort is concerned. But like any staple recipe, it can be good, or it can be GREAT. This best-in-class french onion grilled cheese brings together the best elements of both worlds and really amps up the flavors.

Caramelized onions done right are absolute culinary magic. They have a deep, beautifully balanced sweet and savory flavor combo that just couldn’t be more enticing. You can make them well in advance and assemble and cook your sandwiches right before serving.

What you’ll need

Here’s a glance at the ingredients you’ll need to make this recipe.

ingredients in bowls
  • Gruyere instantly elevates a simple recipe with its umami-forward, nutty, slightly funky flavor. It’s a classic element of French onion soup. If you’d rather have a milder flavor or need this recipe to be vegetarian, you can substitute another variety of Swiss cheese or a mild fontina.
  • Extra-sharp cheddar packs a super-savory, creamy punch and really ties the other elements together.
  • Choose a good-quality, freshly grated parmesan or pecorino. Just a little bit adds a ton of savoriness.
  • Here’s how to make perfect caramelized onions. You can do this well in advance and keep them in the fridge.
  • Any good Jewish-style rye bread or sourdough bread will work well.

How to make it

Here’s an overview of what you’ll do to make a gorgeous French onion grilled cheese. You can see the steps in action in the video that accompanies this post, and get all the details in the recipe card below.

step by step
  1. Mix the filling ingredients in a small bowl.
  2. Spread the mustard on the inside faces of the bread, and top with the filling mixture in an even layer.
  3. Cook, regulating heat, until underside is golden and filling is melting.
  4. Flip once and continue cooking until browned and melty. That’s it!
french onion grilled cheese on a plate with a bite out of it

Expert tips and FAQs

Why the fancy mixing method?

Shredding the cheese and mixing it up with the caramelized onions gives you a consistent, melty, gorgeous tangled mess in every bite. Whenever I make additions to grilled cheese, I like to shred the cheese to make sure it melts well.

Can I make this recipe in advance? What about leftovers?

You can make the caramelized onions a week in advance and store them in an airtight container in the fridge, or even make them up to a year in advance and freeze them. Assemble and cook the sandwiches right before serving.

More favorite hot sandwiches

french onion grilled cheese on a plate with a napkin

Hungry for more?

Subscribe to Umami Girl’s email updates, and follow along on Instagram.

french onion grilled cheese on a plate with a napkin
5 from 4 votes

French Onion Grilled Cheese

By Carolyn Gratzer Cope
French onion soup? Goooood. Grilled cheese? Goooood. French onion grilled cheese? Very, very good. Here's our best-in-class iteration of this mashup of classics. It's super-flavorful and incredibly satisfying, and it can be yours in about 10 minutes. Prepare a batch of caramelized onions in advance and use the rest in the other recipes suggested in that post.
Prep: 5 minutes
Cook: 5 minutes
Total: 10 minutes
Servings: 1
Want to save this recipe?
Enter your email and I’ll send it to your inbox. Plus get great new recipes every week!
Please enable JavaScript in your browser to complete this form.

Ingredients 

  • 1 ounce (28 grams) shredded gruyere cheese
  • 1 ounce (28 grams) shredded extra-sharp cheddar cheese
  • 1 tablespoon (7 grams) grated parmesan or pecorino cheese
  • Pinch of salt, I like using truffle salt when I have it
  • A few grinds of black pepper
  • ¼ cup caramelized onions
  • 2 slices sourdough or rye bread
  • 1 tablespoon (15 grams) dijon mustard
  • 2 tablespoons (28 grams) salted, cultured butter

Instructions 

  • In a small mixing bowl, use a fork to mix together the gruyere, cheddar, pecorino or parmesan, salt and pepper, and caramelized onions. You can gently tease the onions apart with the fork to make sure everything is mixed well.
  • Spread the mustard onto the inside faces of the bread slices.
  • Spread the cheese and onion mixture evenly onto one slice of bread and top with the other slice.
  • In a small frying pan, melt the butter over medium heat.
  • Place the sandwich into the pan and let the bottom slice of bread soak up some of the melted butter. Then carefully flip the sandwich and swipe it around the pan to mop up the remaining melted butter.
  • From this point on, the name of the game is to regulate the heat so that the cheese mixture melts in the same timeframe that the bread becomes golden-brown. You’ll have to use your judgment based on your own stovetop and pan, but this typically means keeping the burner on a medium-low setting.
  • From time to time, use your spatula to press down on the grilled cheese to make sure it’s melting and browning evenly. During cooking (which should take a total of about five minutes), flip the sandwich at least once more to brown the top side. You’re welcome to flip it more if it helps you achieve even melting and browning, but it shouldn’t really be necessary. Toward the end of cooking, you can lower the heat and place a lid on the pan to aid in melting if you like. Don’t leave it on for more than a minute or so, to ensure that the bread remains crisp and doesn’t steam.
  • When cheese is melted and bread is golden-brown, remove the grilled cheese to a cutting board or plate, cut in half and serve.

Step-by-step video

Notes

  1. Gruyere instantly elevates a simple recipe with its umami-forward, nutty, slightly funky flavor. It's a classic element of French onion soup. If you'd rather have a milder flavor or need this recipe to be vegetarian, you can substitute another variety of Swiss cheese or a mild fontina.
  2. You can make the caramelized onions a week in advance and store them in an airtight container in the fridge, or even make them up to a year in advance and freeze them. Assemble and cook the sandwiches right before serving.

Nutrition

Calories: 614kcal, Carbohydrates: 32g, Protein: 15.2g, Fat: 43.5g, Fiber: 4.2g

Nutrition information is automatically calculated, so should only be used as an approximation.

Additional Info

Course: Sandwiches
Cuisine: American
Tried this recipe?Mention @umamigirl or tag #umamigirl!

Hungry for more?

Subscribe to Umami Girl’s email updates, and follow along on Instagram.

Hungry for More?
Subscribe to Umami Girl's email updates, and follow along on Instagram.
Please enable JavaScript in your browser to complete this form.

More Recipes

Carolyn Gratzer Cope Bio Photo

About Carolyn Gratzer Cope

Hi there, I'm Carolyn Gratzer Cope, founder and publisher of Umami Girl. Join me in savoring life, one recipe at a time. I'm a professional recipe developer with training from the French Culinary Institute (now ICE) and a lifetime of studying, appreciating, and sharing food.

Leave a comment

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

Recipe Rating