- 4 large portabella mushrooms, stems removed
- 1 medium red onion, peeled and sliced thin
- 1 tablespoon olive oil
- 1/2 teaspoon salt and pepper
- 1 Chilean Hass avocado
- 4 large hamburger buns
- Broil or grill mushrooms on both sides until just tender, about 5 minutes per side. Sprinkle with salt and pepper.
- Cook onions in olive oil over medium heat until very tender, stirring occasionally, about 10 to 12 minutes.
- Cut avocado in half, remove the pit, and peel and cut into slices.
- Toast buns. Top bun bottom with grilled portabella, 1/4 of the onion and avocado slices. Top with bun top.