Associated Press

Like Philadelphia itself, there is a lot to love about the city’s signature sandwich — the cheesesteak.

But that delicious combination of beef, onions and cheese isn’t the sort of thing you want to pack away every day, unless you’re looking to pack on pounds. So I decided to see if I could make a healthier sandwich that is inspired by the cheesesteak, but is a bit more suited to the everyday.

I started by swapping out the beef in favor of that most steak-like of mushrooms, the portobello. Actually, it’s just the roomy cap of the portobello, filled to the brim with roasted red peppers, grilled scallions, olives and mushroom trimmings, then topped with melted provolone cheese, and lubricated with a little bit of rosemary mayonnaise.

Finally, the whole thing is set on a slice of grilled rustic bread. It may be meatless, but it is not a punk. And heartiness aside, portobellos — like all of their mushroom brethren — are chock-full of nutrients.

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 to prevent the mushrooms from getting waterlogged. In fact, 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.

And that’s the amazing thing about portobellos. Though they have a high water content, if you plunk them into a flavorful marinade, they still absorb it quickly.

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 — like 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.

But however you customize it, I urge you to try adding this super-satisfying vegetarian ringer to the menu the next time you’re grilling up hot dogs and burgers in the backyard, and see if you don’t win some converts.

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OPEN-FACED STUFFED PORTOBELLO SANDWICHES

To remove the gills from the underside of the portobello mushrooms, use a spoon to gently scrape them out.

Start to finish: 40 minutes (25 active)

Servings: 4

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.

Meanwhile, in a small bowl combine the mayonnaise and rosemary, then season with salt and pepper. In a medium bowl combine the peppers and olives, then season with pepper. Set aside.

Spray the scallions with the cooking spray and grill them, turning often, until they are charred on the edges and crisp tender, 3 to 4 minutes. Transfer them to a cutting board and let them cool slightly. Medium chop the scallions and add them to the bowl with the peppers and olives.

Mist the bread with cooking spray, then grill it until it is lightly toasted on both sides. Set aside.

Grill the mushrooms, gill sides down, 3 to 4 minutes. Turn them over and grill on the on the second side until tender when pierced with a knife, another 3 to 4 minutes. Spoon a quarter of the olive-pepper mixture evenly on top of each mushroom. Top with a slice of cheese, cover the grill and cook until the cheese is melted, 1 to 2 minutes.

Spread the mayonnaise mixture on each piece of bread. Transfer each mushroom to one slice of bread. Cut in half and serve right away.

Nutrition information per serving: 380 calories; 230 calories from fat (61 percent of total calories); 26 g fat (7 g saturated; 0 g trans fats); 35 mg cholesterol; 26 g carbohydrate; 5 g fiber; 6 g sugar; 12 g protein; 1,060 mg sodium.

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EDITOR’S NOTE: Sara Moulton was executive chef at Gourmet magazine for nearly 25 years, and spent a decade hosting several Food Network shows. She currently stars in public television’s “Sara’s Weeknight Meals” and has written three cookbooks, including “Sara Moulton’s Everyday Family Dinners.”