Grilled Portobello Burger with Basil Mayo
- Heat grill or grill pan.
- In a small bowl, combine basil, mayonnaise and vinegar; set aside.
- Lightly coat both sides of mushroom caps with cooking spray; season with salt and pepper.
- Grill mushrooms over medium-high heat, until just soft to the touch, about 6 minutes per side.
- To serve, split rolls and toast on grill. Spread a heaping teaspoon of basil mixture on top and bottom halves of rolls. Layer each bottom half with a mushroom, pepper, lettuce leaf and one onion slice; top with remaining half of roll and serve. Yields 1 burger per serving.