This Mushroom Grilled Cheese with Balsamic- Caramelized Onions might be the best grilled cheese you’ve ever tasted!

I like ordinary grilled cheese, but this is no ordinary grilled cheese. This one incorporates caramelized onions flavored with balsamic vinegar and mushrooms that have been sautéed in white wine. You can use Jack or Havarti cheese in this recipe. White cheddar would be good too!

Ingredients Needed:
- olive oil
- onion
- kosher salt and freshly ground black pepper
- balsamic vinegar
- sliced mushrooms
- white wine
- salted butter
- freshly grated Parmesan cheese
- fresh rosemary
- bread
- desired cheese: Jack, Havarti or White Cheddar

How to make Mushroom Grilled Cheese with Balsamic Caramelized Onion:
The complete, printable recipe is at the end of this post.
Prepare the onions: Heat a nonstick skillet to medium; add oil, onions and salt. Sauté the onions over medium to medium-low heat for about 30 minutes, stirring often, until the onions become soft and browned. Add the vinegar and swirl into the onions. Sauté until the liquid is absorbed/evaporated. Let cool.
Prepare the mushrooms: Heat a nonstick skillet to medium; add oil, mushrooms, salt and pepper. Sauté the mushrooms over medium heat for about 10 minutes, stirring often, until they are softened. Add the wine and sauté until the liquid is absorbed/evaporated. Let cool.
Prepare the butter: Mix butter ingredients in a small dish.
Assemble and grill the sandwich: (These are instructions for one sandwich, then repeat to make another): Spread butter on 2 slices of bread. Place the bread, butter-side-down, on a nonstick skillet. Top with a layer of cheese, then ½ of the onions, then ½ of the mushrooms. Add a second layer of cheese on top of the mushrooms. Add the 2nd slice of bread, butter-side-up, and set the pan over medium heat. Place a lid on top. Watch it closely. You want it just toasted and cheese beginning to melt before you flip it. Use a spatula to peek underneath, and adjust heat as needed. Flip and toast the other side. When properly toasted on both sides, remove to a plate, slice and eat. Repeat to make a second sandwich.

Tips and Substitutions:
- Use sweet yellow onions for the best, sweetest flavor in your caramelized onions.
- If you don’t cook with wine, it’s okay to use chicken broth in place of the wine in making the sauteed mushrooms.
- Be creative with your cheese choice!

What I Love About This Recipe:
- It’s a major win for grilled cheese and mushroom lovers!
- It’s so gourmet that you can serve it for dinner too.
- Every part of this sandwich is delicious.
Favorite Sandwich Recipes:

Mushroom Grilled Cheese with Balsamic Caramelized Onions
Ingredients
BALSAMIC CARAMELIZED ONIONS:
- 1 tablespoon olive oil
- 1 medium onion, sliced thinly
- 1 pinch kosher salt
- 2 tablespoons balsamic vinegar
SAUTEED MUSHROOMS:
- 1 tablespoon olive oil
- One 8-ounce package sliced mushrooms
- ¼ teaspoon kosher salt
- freshly ground black pepper
- ¼ cup white wine
BUTTER:
- ¼ cup (½ stick) salted butter, softened
- 2 tablespoons grated Parmesan cheese
- 2 teaspoons chopped fresh rosemary
SANDWICHES:
- 4 slices bread
- 4 ounces jack, havarti or white cheddar cheese, sliced
Instructions
- Prepare the onions: Heat a nonstick skillet to medium; add oil, onions and salt. Sauté the onions over medium to medium-low heat for about 30 minutes, stirring often, until the onions become soft and browned. Add the vinegar and swirl into the onions. Sauté until the liquid is absorbed/evaporated. Let cool.
- Prepare the mushrooms: Heat a nonstick skillet to medium; add oil, mushrooms, salt and pepper. Sauté the mushrooms over medium heat for about 10 minutes, stirring often, until they are softened. Add the wine and sauté until the liquid is absorbed/evaporated. Let cool.
- Prepare the butter: Mix butter ingredients in a small dish.
- Assemble and grill the sandwich: (These are instructions for one sandwich, then repeat to make another): Spread butter on 2 slices of bread. Place the bread, butter-side-down, on a nonstick skillet. Top with a layer of cheese, then ½ of the onions, then ½ of the mushrooms. Add a second layer of cheese on top of the mushrooms. Add the 2nd slice of bread, butter-side-up, and set the pan over medium heat. Place a lid on top. Watch it closely. You want it just toasted and cheese beginning to melt before you flip it. Use a spatula to peek underneath, and adjust heat as needed. Flip and toast the other side. When properly toasted on both sides, remove to a plate, slice and eat. Repeat to make a second sandwich.
Nutrition
Nutrition information is automatically calculated, so should only be used as an approximation.
Horseradish cheddar. That would make an awesome roast beef melt sandwich. I have got to try those cheeses. They all sound wonderful.
It’s hard to pick just one, but I love Humboldt Fog.
Sartori Sarvecchio Parmesan.
The best cheese I’ve ever tasted was an Irish cheddar. I tried it at Jungle Jim’s grocery emporium in the Cincinnati area. They have more varieties of cheese (and so many other things) than I’ve ever seen anywhere else.
We eat a lot of grilled cheese! One of my faves is rye bread with fontina cheese and roasted red pepper with a good olive oil. Simple but tastes delicious.
I love cheese and have tried many types but i never realized that there were so many varieties with inclusions as you have to offer. These looks wonderful.
I like a nice smoked cheddar!
I love all cheese but good ole fashioned sharp cheddar is my favorite!
This looks absolutely delicious. Thanks for sharing.
Great pictures too. 🙂
Carol L
One of the best cheeses is a Monteray Jack we had not so long ago. But we’re cheese lovers here and they are all delicious.. 🙂
Carol L