Despite the research and years of experience that went into creating Burger 21, the concept’s president has been surprised by one aspect of the business: the brand’s broad consumer appeal.

“The amazing thing we didn’t predict was so many parties coming in with three generations,” says Mark Johnston, chief concept officer of Front Burner Brands and president of Burger 21. “Kids, parents, and grandparents all find something they love.”

Front Burner Brands is the management company for The Melting Pot Restaurants Inc., Burger 21, and a six-unit, full-service Tampa, Florida, chain called GrillSmith. Johnston says when he and his partners decided to create a fast-casual concept, offering enough variety to eliminate the veto vote was one of their main goals.

“We wanted to have a burger place with something for everyone,” Johnston says. “So we included a big variety, including some healthy options.”

He puts Burger 21 in a category he calls the “beyond-the-better-burger” segment.

At Burger 21, orders are placed at the counter, but then the experience becomes more like a full-service restaurant. Employees called “movers” bring food to the table and ask if diners need anything brought to them, like sauces or drink refills.

Guests wait for their food at their table or visit the sauce bar and load up on the 10 dipping sauces offered. These range from ketchup and mustard to more unusual options like Thai ketchup and a Ragin’ Cajun dip. There are two sauces developed for Burger 21’s sweet potato fries: Apple Cider and Toasted Marshmallow.

Burger 21 customers can also hang out at the brand’s shake bar and watch as ice cream concoctions are made by hand.

“We have a modern version of an old-fashioned soda fountain with 10 barstools where we make shakes, floats, sundaes, and fresh-baked cookies,” Johnston says.

A typical 2,400–3,000-square-foot location has five different types of seating, from outdoor patio seating to traditional booths, banquettes, four-tops, and high-tops, as well as the shake bar.

As its name implies, Burger 21 offers 21 burgers: 10 beef and 10 non-beef, including chicken, turkey, shrimp, and veggie. On the 21st of every month, a new burger that’s not on the regular menu is featured.

The best seller is the Cheesy Burger, which, like all Burger 21 beef options, is made with certified Angus beef. It’s topped with lettuce, tomato, and a choice of American, Cheddar, or Swiss cheese and served on a toasted brioche bun. Applewood-smoked bacon is added to create the No. 2 seller, the Cheesy Bacon. The rest of the beef burgers, however, depart from tradition. The Tex-Mex Haystack, for example, includes lettuce, tomato, bacon, Gouda, guacamole, onion strings, and chipotle-jalapeño sauce.

In the non-beef category, the Chicken Marsala burger is made with hand-ground chicken combined with pieces of diced chicken breast before being formed, seasoned, and lightly breaded in Panko breadcrumbs. It is topped with sautéed mushrooms and a Marsala wine sauce. The Ahi Tuna is made with Panko-crusted, sushi-grade ahi tuna that is lightly fried and topped with lettuce, tomato, sriracha aioli, caramel soy, avocado, and pickled cucumber, all served on a toasted sesame bun.

Hot dogs are served on grilled split lobster rolls. Other choices include chicken tenders, sliders, and six different salads.

For dessert, in addition to shakes in traditional flavors like chocolate, vanilla, and strawberry, Burger 21 offers Signature Shakes in flavors like Bananas Foster, Crème Brûlée, and Ybor City Double Espresso. Other indulgences include sundaes and retro floats made with gourmet bottled sodas.

An average per-person ticket at Burger 21 is $10.70. The stores are open from 11 a.m. to 9 or 10 p.m., depending on location, with about 40 percent of sales occurring during the lunch period and 60 percent at dinner.

“We choose densely populated residential locations that also have a good daytime population,” Johnston says. “We do a good lunch trade every day … even on Saturday and Sunday.”

Burger 21 opened its first location in the Tampa area in 2010. A second unit opened about six miles away from that first store in 2011. After two more corporate stores opened in 2012, the first franchised unit opened in Orlando in late 2012.

Johnston says 10–14 stores are slated to open in 2014. “Our goal is to sell 25 more units this year on top of those in development,” he says. “I think we’ll have 500 stores open in seven to 10 years.”

Development has been primarily in Florida so far, but expanded into Georgia, North Carolina, and Virginia, along with movement into the Northeast, with two locations in New Jersey and New York. Johnston says stores are in development in Arizona, and Texas and Colorado are target markets.

“We can really go anywhere in the contiguous 48 states because we have such a variety of locations for The Melting Pot restaurants that we have distribution systems everywhere,” Johnston says.