But these big mushrooms have to be cleaned before they can be savored. Start by removing the dark gills on the underside, lightly scraping them out with a teaspoon. Then simply rinse the cap on both sides under cold running water to remove any dirt. I know that some folks advise against rinsing, preferring instead to wipe away the dirt with a damp cloth. A quick rinse doesn’t harm them and it’s infinitely quicker and more thorough than wiping them clean. Just pat the caps dry afterward so they’ll be able to absorb the marinade.
Topping-wise, I’ve gone the Mediterranean route, but you’re welcome to substitute the toppings of your choice. Maybe you’ll want to grill and chop up some complementary mushrooms — such as shiitake or oyster — and put them on top of the portobello. Maybe you’ll opt to top it off with grilled broccoli, asparagus or onions. Likewise, if you’re not crazy about provolone, you can swap in thin slices of mozzarella, cheddar or Italian fontina. Finally, if don’t like mayo on your sandwiches, don’t use it. Dijon mustard works very nicely in its place.
Open-Faced Stuffed Portobello Sandwiches
Start to finish: 40 minutes (25 active); Servings: 4
To remove the gills from the underside of the portobello mushrooms, use a spoon to gently scrape them out.
1 garlic clove, minced
1 tablespoon Dijon mustard
2 tablespoons sherry vinegar
2 tablespoons extra-virgin olive oil
Salt and ground black pepper
4 large portobello mushrooms, stems and gills discarded
1/2 cup light mayonnaise
2 teaspoons finely minced fresh rosemary
Olive oil cooking spray
1/2 cup medium chopped jarred roasted red peppers
1/2 cup pitted black olives, medium chopped
6 large scallions, bottoms trimmed
4 slices rustic whole-grain bread
4 thin slices provolone cheese (about 3 ounces total)
Heat the grill to medium.
In a small bowl, combine the garlic, mustard, vinegar, olive oil, and a hefty pinch each of salt and pepper. Brush the marinade on both sides of the mushrooms, then transfer them to a zip-close plastic bag, along with any remaining marinade. Let them marinate at room temperature for 20 minutes.