Portobello Mushroom Burger

This delicious vegetarian burger features a juicy portobello mushroom cap marinated in balsamic vinegar and grilled to perfection.

Ingredients - Serves 2

In a small bowl, whisk together the balsamic vinegar, olive oil, minced garlic, salt, and pepper.
Remove the stems from the portobello mushrooms and brush both sides with the marinade.
Let the mushrooms marinate for at least 10 minutes.
Preheat the grill or grill pan over medium heat.
Grill the mushrooms for about 5 minutes per side, or until they are tender and juicy.
While the mushrooms are grilling, toast the burger buns on the grill for a minute or two.
Spread mayonnaise and mustard on the bottom half of each bun.
Place a grilled portobello mushroom on each bun, and top with lettuce, tomato, red onion, and avocado slices.
Cover with the top half of the bun and serve immediately.