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Portobello and Havarti Burgers with Caramelized Onions

Portobello and Havarti Burgers with Caramelized Onions

We love portobello burgers. I like to use different herbs, vegetables, and cheeses to enhance the flavor of the mushroom. In this burger, I used Havarti cheese, caramelized onions, fresh basil, and roasted garlic mayonnaise. It was light, flavorful and so delicious. You don’t always have to use meat to make a fantastic burger!

How to Make Portobello and Havarti Burgers with Caramelized Onions


  • 1 sweet yellow onion, sliced thinly
  • 2 tsp olive oil
  • 4 large portobello mushrooms, stems removed and cleaned
  • 4 slices of Havarti cheese
  • 4 hamburger buns
  • Tomato slices
  • Fresh basil leaves

Heat olive oil in a skillet over medium heat. Add onions and saute until caramelized and tender – about 25-30 minutes, making sure to stir frequently. Season with sea salt to taste. Set aside when finished.

Mushroom Marinade:

  • 1/4 cup of balsamic vinegar
  • 1 tbsp olive oil
  • 1 tbsp fresh basil leaves, chopped finely
  • 1 clove of garlic, minced
  • Sea salt and fresh cracked pepper to taste

Marinate the mushrooms in a large zip lock bag for 15-20 minutes prior to cooking. Heat the same skillet, that the onions were cooked in, over medium heat. Once the skillet is hot, place the mushrooms in, top side up. Cook for 4-5 minutes then flip. Pile the caramelized onions onto the mushroom then place Havarti cheese and cook for an additional 4-5 minutes.

Roasted Garlic Mayonnaise:

  • 1 bulb of roasted garlic (see recipe here)
  • 2 tbsp mayonnaise
  • Sea salt and fresh cracked pepper to taste
Mix roasted garlic with mayonnaise then season with sea salt and freshly cracked pepper, to taste.

Spread the garlic mayonnaise on each side of the toasted bun, add the mushroom then top with tomato slices and basil. Enjoy!

Portobello and Havarti Burgers with Caramelized Onions

Click here for a printable version of this recipe

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  1. Mmmm … extra m’s on this one. Your marinade and mayo sound terrific! My hubby loves caramelized onions on his “burgers”. The havarti/portobello combo sounds great! Your plating looks beautiful, too! Great looking tomatoes and basil!

  2. You’re so right. Sometimes a big, juicy Portobello beats meat, hands down.

    The juice they let go into the bread is incredible ,isn’t it?

  3. I like the inclusion of basil leaves as a substitution for lettuce. Other leafy herbs could work as well.

  4. I couldn’t agree with you more. While I love a good beef burger, a portobello or veggie burger can be just as satisfying. Yours looks delicious!

  5. This looks and sounds delicious, I love caramelized onions on burgers.
    I like the sound of that garlic mayo, too.

  6. i have never tried making mushroom burgers yet..but when i saw all the ingredients you used..i salivated immediately!! this sounds a fantastic burger that could definitely kick the ass of MCdo LOL!!!! i love it

  7. Mushrooms are one of my favorite things and a marinated portobello mushroom burger sounds really good!

  8. LOVE TIS portobello burger. The marinade is perfect! I used Greek yogurt with a Parmesan spice added for the aoli. it was delicious and a little lower in calories. Thanks for this simple yet decadent recipe! Making it again tonight for meatless Mondays!

  9. YUM! Although I’m not a vegetarian, this ‘Burger’ had my name all over it. It’s everything I love, all in one delicious package. I used our local bakery’s Poppy Seed Buns, but otherwise followed the recipe – which was perfect. Hubby (a huge meat eater) enjoyed ’em, as well as our young kiddoes, who’s little tummies could each only eat 1/2. This ‘Burger’ is now on rotation for our Burger/Sandwich nights. I serve them with Oven Baked Sweet Potato Fries. Thank you for ALL of your lovely recipes.

    1. Angelina,

      I’m so happy you all loved this portobello burger–it’s one of my very favorites. Thank you for your kind words and for being a loyal reader.