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!

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

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