For cooking at home – preheat an oven to 400 F (210 C). You could also cook this recipe over a charcoal or gas grill or even a campfire. Place whole, washed 3-ounce portobello caps on individual squares of aluminum foil. Remove the stems from each mushroom cap and flip them over. Rub a ¼ teaspoon of olive oil into each mushroom cap.
Step 2
Flip the mushroom caps back over. Slice a ¼”-thick slice of tomato for each mushroom cap you have. If you don’t have heirloom tomatoes, beefsteak tomatoes are another large variety of tomato you can use. Lay a large tomato slice on top of each mushroom cap. Season each tomato slice with pinches of salt and pepper, then lay two slices of mozzarella cheese on top of each mushroom.
Step 3
Fold your aluminum foil squares to fully wrap each mushroom cap with tomato and cheese. Place the wrapped mushrooms onto a heat-safe tray before putting them in your oven. Bake the wrapped mushrooms for 25 minutes. If making the mushrooms on a grill, your cooking time will vary. If cooking over a campfire, you will still need to place the wrapped mushrooms on some sort of tray over the flames. Carefully unwrap before eating hot.