- 2 tablespoons olive oil
- 2 tablespoons balsamic vinegar
- 1 tablespoon Dijon mustard
- 2 cloves garlic, minced
- 1/2 teaspoon Worcestershire sauce (optional)
- 1 pinch salt and ground black pepper
- 4 large portobello mushrooms, stems removed
- 4 kaiser rolls, split
- Preheat grill for medium-high heat and lightly oil the grate.
- Whisk olive oil, balsamic vinegar, Dijon mustard, garlic, Worcestershire sauce, salt, and pepper in a bowl. Brush the mixture over the tops and bottoms of the mushrooms; let stand for 10 minutes.
- Grill mushrooms on the preheated grill with the cover closed until mushrooms are browned and tender, about 10 minutes, turning once. Serve on kaiser rolls.