Directions 11 steps | 45 Minutes
Use a paper towel to wipe off the top of the mushrooms. Gently scrape off the gills on the inside of mushrooms with a spoon and discard.
Brush both sides of the mushrooms with olive oil. Place on a platter and season with salt and pepper.
Place the mushrooms bottom side up and drizzle the balsamic vinegar on top. It will pool slightly in the cap of the mushroom. Let the mushrooms sit in this marinade for 20 minutes or up to 4 hours.
While the portobello mushrooms are marinating, make the garlic aioli. Mix the mayonnaise, minced garlic and lemon zest together until combined. Season to taste with salt and pepper. Set aside.
Heat a grill or a stovetop grill pan on medium-high heat. You can also use the broiler setting on your oven. Once hot, place the mushrooms, bottom side up, on the grill. Cook for about 3-4 minutes, or until grill marks form.
Flip the mushrooms and cook for another 3-4 minutes or until semi-soft.
Remove from heat and place one slice of cheese on each mushroom. Cover loosely with aluminum foil. Keep warm.
Place the onion slices on the grill and cook for about 2-3 minutes on each side. Keep warm.
To assemble the sandwiches, put the bottom slice of focaccia bread on a plate. Spread a layer of garlic aioli.
Top with mushroom and cheese, roasted pepper, onion and lettuce.
Spread more aioli on the top slice of bread and place on top of the sandwich. Serve Immediately. Enjoy!
- Use blue or goat cheese for a stronger, more pungent flavor.
- Serve on a brioche bun instead of focaccia bread.
- Make truffle aioli with ½ cup mayonnaise and 1 teaspoon of truffle oil.
- Add jalapeño slices or grilled jalapeños
- The aioli can be made up to 1 week in advance. Keep refrigerated.