PORTLAND — On the edge of the city, two teenagers in a truck scoop rich chocolate ice cream onto freshly baked peanut butter cookies. Though it looks fun, they have 600 more to go.

The decadent creation, called The Buckeye, is one of three gourmet ice cream sandwiches being sold on the streets of Portland this week from the city’s newest food truck, Mainely Treats.

Run by childhood friends Jack Barber and Ben Berman of Cape Elizabeth, the ice cream sandwich, sundae and root beer float truck is the third mobile canteen in their fleet.

“We are taking a classic ice-cream truck idea and doing something totally different,” said Berman, whose mission is to find “combinations that people haven’t seen before.”

Following the success of Mainely Burgers, their popular burger truck that debuted at Scarborough Beach on Memorial Day weekend 2012, Mainely Treats launched on July Fourth at the Eastern Promenade. On a hot night, the reception was explosive.

“We are very happy that we sold a lot of ice cream sandwiches,” to more than 500 customers, said Berman, who served almost as many root beer floats. “We hit all our numbers.”

The best response was from a fan on Twitter.

“Someone tweeted that they woke up dreaming of our ice cream sandwiches,” Berman said.

Crafting an upscale beach treat means sourcing “the best products available,” said Berman.

Using ice cream from Mount Desert Island Ice Cream in Bar Harbor and cookies from Blue Rooster Food Co. in the Old Port, the 20-year-olds are adding a gourmet spin to the familiar Good Humor staples.

Flavors such as banana hammock — banana molasses ice cream between Snickerdoodle cookies — are $4 each. The bright blue truck also features root beer floats with Capt’n Eli’s Root Beer, made by Shipyard Brewing Co., and a scoop of Jack Daniels ice cream. Brownie ice cream sundaes round out the offerings.

The summertime treats were a natural next step for the young entrepreneurs.

“Burgers were superaccessible food for all types of people. We wanted to elevate that in some way,” said Berman.

The ice cream treats will be offered at Scarborough Beach and on their food trucks cruising Portland this summer.

As the city’s fledgling food truck scene starts to rev up — this is the first summer mobile food vendors are taking advantage of new permitting — the partners, who have known each other since they were 6, are doing more than adding to Portland’s hot culinary scene. They are creating jobs and doing their part to keep their peers here.

“We’ve made it our goal to hire young people,” said Berman. ”I think in some small way we are hoping to fill what they are calling the skills gap in Portland by telling people that would be going to Boston or D.C. for jobs or internships to come work with us,” said Berman.

While attending school in Boston — Berman at Tufts University and Barber at Babson College — the pair, who will be juniors this fall, became enamored with Boston’s buzzing food truck niche.

But instead of jumping into the fray there, they decided to bring some of that excitement home.

Last spring Berman and Barber approached the concession stand at Scarborough Beach State Park, convincing management they could provide a better, more affordable and locally sourced menu.

Impressed by their chutzpah, manager Seth Sprague took note.

“They had no experience, no track record, were still in college. But we were convinced that they had the energy, drive and entrepreneurial spirit,” said Sprague. “We took a chance on them and they have done a great job.”

In a trailer next to the concession stand, they flipped burgers, added gourmet toppings and soon took over the stand, too. At the end of the summer they took stock and realized they had a solid baseline and a scalable business.

“We realized we [could] duplicate this and bring it to Portland,” said Berman.

WIth family financial backing, they launched their second truck in March and made it their mission to create jobs for their generation. They now have 16 employees, all 20 and under.

But running a successful mobile food business is filled with obstacles. From finding the right truck to installing the right equipment to training staff in a tight space, “there is no direct path. Nothing that we’ve done has been standard,” said Berman.

But they learn with each mile they traverse.

“Every step of the way we are building new relationships,” said Barber.

And as with anything new, not all restaurant owners have been overjoyed by the arrival of food trucks. But the city’s food culture is so vast there’s enough room for meals on wheels and bricks and mortar restaurants to coexist, these newcomers say.

“We don’t see why someone can’t grab a burger at a food truck for lunch and walk around the city and have a nice dinner at Fore Street,” said Berman, referencing one of Portland’s best-known restaurants. “We are filling a void in areas of the city where there are not many options.”

Upon hearing about their newest product line, customers were eager for more.

“Who doesn’t want ice cream on a hot day right after a burger?” said Marty Tauver, who traveled from Biddeford to Portland for a Mainely Burger. “It goes hand in hand.”