Preheat an outdoor grill for medium heat and lightly oil the grate.
Whisk vinegar, oil, and garlic together in a small bowl.
Arrange mushrooms on a baking sheet with the gills facing up; brush with about 2/3 of the marinade and let sit for 3 to 5 minutes.
Transfer mushrooms to the preheated grill with the gills facing down; grill, basting occasionally with remaining marinade, until tender, about 4 minutes per side.
While the mushrooms are cooking, mix mayonnaise, basil, Dijon, and lemon juice together in a small bowl. Butter toasted rolls, then spread with mayonnaise mixture.
Remove mushrooms from the grill and place on bottom buns. Top with lettuce, tomatoes, and top buns.
Nutritional Facts
Per 6 servings
Calories: 412
Carbohydrate: 36g
Fat: 28g
Fiber: 4g
Protein: 8g
Sugar: 8g
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