Portabella Mushroom Burger with Grilled Sweet Onions
- 3 teaspoons olive oil, divided
- 1 teaspoon Balsamic vinegar
- 4 large Portabella mushrooms
- 2 thick slices sweet onion
- 4 whole wheat hamburger buns
- 1/2 cup packed baby spinach leaves
- 4 teaspoons soft goat cheese
- Salt and pepper
Prepare grill for high heat. In a small bowl, mix together 2 teaspoons olive oil and balsamic. Lightly score mushroom top. Brush mushrooms and onion with vinaigrette and sprinkle lightly with salt. Brush onions with remaining teaspoon olive oil and sprinkle with salt. Place mushrooms and onion on grill. Grill until mushrooms and onion are soft, turning once, about 4 minutes for mushrooms and 6 minutes for onions. Remove mushrooms and onion from grill and place on a plate. Grill buns.
- Spread goat cheese on cut sides of each bun.
- Season with salt and pepper if desired.
- Top bottom bun with one mushroom, onion slice, second mushroom, and spinach.
- Place top bun on and serve immediately.