Ingredients:
- 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.
Toast the buns.
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 toasted bun, add the mushroom then top with tomato slices and basil. Enjoy!