The Best Grilled Portobello Mushroom Burger Adapted from https://www.skinnytaste.com/the-best-grilled-portobello-mushroom/ Servings: 4 INGREDIENTS 4 portobello mushroom caps 2 tbsp balsamic vinegar 1 tbsp soy sauce 1 tbsp olive oil 1 tbsp chopped rosemary 1-1/2 tsp steak seasoning like Montreal Steak STEPS 1) In a large bowl, whisk together vinegar, soy sauce, oil, rosemary, and Montreal steak seasoning. 2) Place the mushroom caps in the bowl and toss with sauce, using a spoon to evenly coat. Let stand at room temperature for 20 to 30 minutes, turning a few times. 3) Heat the grill or indoor grill pan over medium heat. When hot, brush the grate with oil or lightly spray the grill pan. 4) Place the mushrooms on the grill, reserving marinade for basting. Grill for 5 to 7 minutes on each side, or until tender, brushing with marinade frequently.