Mac ’n’ cheese and grilled cheese are the quintessential American comfort-food favorites. And recently, both have gone gourmet in the fast-casual industry as diners look for nostalgia and taste excitement all in the same bite.

Menu mentions for mac ’n’ cheese have risen 33 percent over the past five years, according to research from the Wisconsin Milk Marketing Board (WMMB).

Grilled cheese has also enjoyed a heyday as of late, as many food-truck concepts slinging the sandwich open brick-and-mortar locations and more operators explore opening restaurants with a single menu focus. Like mac ’n’ cheese, grilled cheese has become a fixture in the fast-casual scene, with concepts like The Melt, Melt Shop, Roxy’s Grilled Cheese, American Grilled Cheese Kitchen, Cheeseboy, UMelt, Melt Mobile, and The Grilled Cheese Truck focusing primarily on everyone’s favorite melt sandwich.

But it’s not all about simply slapping cheese in between two pieces

of buttered bread, or throwing it into pasta. These chains have figured out that in order to attract customers, they need to step up their game several notches with classic cooking techniques, a focus on quality ingredients, and innovation in the form of fun fixings and pairings.

“Grilled cheese is magical; everyone can relate to it,” says Nate Pollak, co-owner of American Grilled Cheese Kitchen in San Francisco, which serves the popular sandwich along with a daily mac ‘n’ cheese. “People often told me I was crazy for opening a grilled cheese restaurant because they can make the sandwich at home. We’re not trying to compete with what you do at home, because what we do at American Grilled Cheese Kitchen is something you can’t or don’t want to do at home.”

The same could be said about mac ’n’ cheese; the first versions people eat as kids usually come out of a box. But such seemingly simple dishes are anything but in the restaurant community. Here, operators and chefs break down the potential of enhancing these humble comfort foods.

The cheese

For both mac ’n’ cheese and grilled cheese, experts say, it’s all about “meltability.” While American and Cheddar cheese continue to be the most popular cheeses on grilled cheese sandwiches, the fastest-growing alternatives are, in order, white Cheddar, Muenster, Fontina, Monterey Jack, Brie, Provolone, and Swiss, according to research from the WMMB.

Much like grilled cheese, semi-soft cheeses work best for mac ’n’ cheese. Colby, Havarti, Gouda, Mozzarella, and Fontina all work well, but there has been an uptick in the use of alpine-style, smoked Gouda, and even blue and Gorgonzola cheeses for extra flavor, says Heather Porter Engwall, a spokeswoman for the WMMB.

At American Grilled Cheese Kitchen, mac ’n’ cheese starts off as a classic roux-based béchamel sauce spiked with shreds of cheese left over from the grilled cheese menu. Those include Cheddar, Monterey Jack, Havarti, Gouda, Gruyere, Mozzarella, and smoked Mozzarella, as well as, in some creations, a sage-infused young cow’s milk cheese from a local creamery.

“With aged cheese, you might end up with a non-melted sandwich, and spreadable, creamy cheeses can turn into oil when exposed to 500-degree heat. So you have to be very careful in the selection of cheeses,” says Heidi Gibson, chef and co-owner.

Inspired by a Gorgonzola gnocchi dish at another restaurant, Gibson sought to add the pungent cheese to a new sandwich creation, but knew she had to tone down the strong flavor. “People either love or hate blue cheese, so we created a compound butter with fresh sage to add extra flavor and paired a milder, Italian Gorgonzola with a really mild Monterey Jack or Havarti,” she says.

Mac ’n’ cheese also has limitations when it comes to certain cheeses.

“American Feta cheese has a nice salt content, but we had to spend a little extra money to buy a good French or Bulgarian Feta, because it is less dry,” says Lorraine Platman, founder of Sweet Lorraine’s Fabulous Mac n’ Cheez, which is based in Michigan. Alternatively, Chevre goat cheese works well as a creamier mac ‘n’ cheese, as does fresh Mozzarella, but only when crumbled rather than added as slices, she says.

Other cheeses like Mozzarella, Pepper Jack, Emmental, and Swiss are added in shredded form, but there are sticking points with that, too. “We shred our own cheese rather than purchase it from companies, because we found they were adding things like cellulose or corn starch to prevent caking, and we are very into truth in advertising and knowing exactly what is in the food we serve,” Platman says.

The construction

When it comes to creating the best mac ’n’ cheese, Platman has a few tricks up her sleeves after decades of perfecting the craft.

“It seems counterintuitive, but you actually don’t want to cook the pasta in salted water because, as it evaporates, it changes the taste profile, and this way you have more control over the salt in the dish that’s already salty because of the cheese,” she says.

It’s also important to thoroughly drain the pasta once cooked, or you risk diluting and breaking the delicate cheese sauce. Platman teaches her staff to let the pasta drain longer in the colander rather than quickly transferring it to the cheese sauce. “Everyone is really busy and just wants to make the dish, but this makes a huge difference,” she says.

At Sweet Lorraine’s, the classic béchamel base gets a blast of shredded, ultra-sharp Cheddar cheese before mixing with the smaller, “twisted” noodles and toppings. It’s then set under the broiler for one minute to melt. For breadcrumbs, Sweet Lorraine’s uses day-old herb and olive oil focaccia for extra flavor.

When it comes to grilled cheese, drawing moisture out is also just as important. “Even simple grilled cheese is a lot of science,” Gibson says. To draw out moisture from fillings like tomatoes, mushrooms, and olive spread, she creates a barrier by layering the cheese slices on the outside in a bread, cheese, filling, cheese, bread construction. “Putting the cheese on the outside also helps it melt thoroughly,” she says.

Equipment matters, too. At UMelt in Providence, Rhode Island, co-owners Ben Wood and Jonathan Kaufman use commercial-grade, flat panini grills rather than griddles to avoid the need to flip the sandwiches and to cook them in a swift four minutes or less. But the double-sided presses also have a different function: They help squeeze together the cheese with different fillings of all flavors and textures to create a package that is crispy on the outside.

Sweet Lorraine’s and American Grilled Cheese Kitchen even combine mac ’n’ cheese and grilled cheese into one item. At Sweet Lorraine’s, the mac ’n’ cheese is left to cool and stick together slightly, then re-melted when enclosed with two pieces of brioche bread. At American Grilled Cheese Kitchen, Gibson forms the cooled mac ’n’ cheese into patties, layers each side with cheese slices, then bakes the sandwich in the oven to avoid spillover and extra mess.

The fixin’s

Because mac ’n’ cheese in a grilled cheese sandwich isn’t always enough to grab customers’ attention, UMelt offers its “White Trash” concoction with a 12-hour house-roasted pork, homemade barbecue sauce, and extra Cheddar, all of it piled on sourdough.

The beauty of grilled cheese is the variety and flexibility it provides, Wood says. “It’s easy to pair bread and cheese with a lot of different ingredients,” he says. “We’re right across the street from [culinary school] Johnson & Wales, where a lot of our staff members come from, and [Kaufman] and I have a deep food background. So we are always collaborating as a team to come up with new ideas.”

Dave Danhi, owner of The Grilled Cheese Truck, which has trucks in Los Angeles, Phoenix, New York, and Austin, Texas, also experiments with sandwich toppings. His biggest hit, and one that’s appeared on multiple food shows, is the Cheesy Mac & Rib sandwich, a pressed sandwich filled with smoked pulled pork, mac ’n’ cheese, caramelized onions, and sharp Cheddar.

“Unless you keep kosher or are vegetarian, this one is hard to stay away from,” Danhi says. “There is a lot of love in that sandwich.” As there is in his Smothered Pork Grilled Cheese. Instead of a heavy gravy and thick pork chop, Danhi chops up the loin into bite-sized portions and then serves it with a beet applesauce and optional lighter gravy made from the cooking juice.

At American Grilled Cheese Kitchen, Gibson finds inspiration in favorite dishes she’s tried while dining out at restaurants around the world. Then it’s a matter of some good R&D to convert that into a working grilled cheese sandwich. For a Hawaiian pizza grilled cheese, she roasts pineapple and tomatoes to draw out the moisture, then pairs that with fresh Mozzarella, Fontina, and ham slices sprinkled with a little chili flakes and oregano, again using her trick of layering the sandwich with the cheese on the outside. For a more traditional pizza version, she’ll serve the homemade marinara sauce on the side for dipping, rather than adding it to the sandwich, which has Mozzarella and Fontina for a little extra “stink.”

For a play on a creamy wild mushroom and Gruyere pasta dish she once had, Gibson used a variety of exotic and seasonal mushrooms, which she sliced raw and layered in between the Gruyere. The rapid-cook oven cooked the mushrooms while melting the cheese. Gibson switched to this method after finding it was too difficult to maintain the consistency of a roasted mushroom duxelle (a chopped mushroom dish).

Compound butters are another trick for adding flavor to grilled cheese. In addition to the sage butter American Grilled Cheese Kitchen uses, Gibson has added other herbs like rosemary and thyme, and spices like chipotle and cayenne. But she’s careful not to add anything with sugar (like maple) for risk of burning.

At UMelt, a tomato basil sandwich has Narragansett fresh Mozzarella from a local creamery; a homemade, nut-free basil pesto; and fresh tomatoes from the restaurant’s own onsite garden. UMelt also pairs crunchy, sweet sliced green apple with creamy Havarti, caramelized onions, and turkey that’s roasted onsite and sliced.

Poultry has made its way onto more grilled cheese sandwiches. At Melt Shop, fried chicken pairs with buffalo sauce, Pepper Jack, and blue cheese for another twist on wings. A similar fried chicken grilled cheese sandwich swaps buffalo sauce for smoky Melt Sauce, similar to a chipotle mayo, and pairs with crunchy slaw for a Southern-style version.

Even for mac ’n’ cheese, chicken surprisingly beat out bacon and even lobster as the most popular protein add-ins, according to research from the WMMB. Sausage, shrimp, crab, pork, ham, and beef followed those ingredients as the most popular.

At Sweet Lorraine’s, Platman has added all of the above to her mac ’n’ cheese over the years, but has won awards for her pesto-based mac ’n’ cheese with spinach, toasted walnuts, Parmesan, and garlic to avoid allergens while adding more flavor and color to the generally “beige” dish.

She often uses steak combined with onions and peppers in fajita form. All of it’s broiled with Pepper Jack cheese and topped with a homemade pico de gallo. Chorizo is a popular protein alternative, as is baked tofu for vegetarians. And for a take on a cheesesteak, Platman has combined Philly beef sautéed with bell peppers and onions, melted Cheddar, and Italian peppers. “We’re not subtle; we want the flavors to be big and bold,” she says.

That’s the key when it comes to upping the quality of staples like mac ’n’ cheese and grilled cheese: Go big or go home.