Rebecca Roth Gullo and Seth Yaffe work in the same restaurant and live blocks away from each other. But it took them traveling separately nearly 1,000 miles to Chicago to hatch the idea for Blackbird, the Gallows Group’s doughnut and coffee shop slated to open this month in the South End.

In the spring of 2013, owner Gullo stopped by the Doughnut Vault in Chicago, a couple of months after COO Yaffe had made the trek. Customers have been known to line up before sunrise to grab a round treat from the famed shop, which often sells out.

“I got a phone call from [Gullo] saying, ‘Oh my God, this is the best thing I’ve ever eaten. Guess what, we’re opening a doughnut shop,’ ” Yaffe says. “For me, it was life changing. Doughnuts around here were Dunkin’ Donuts, or once in a while you’d go to a bakery that was doing other things but happened to have a doughnut there.”

Ahead of what would become a national craze for the pastry, the group soon started adding doughnuts to the Gallows menu and visiting other shops and bakeries to get a better feel for the breakfast staple.

Memories of those visits prompted a last-second design change mere days before Cafco Construction started the project in November. Out went the books and curios, part of an initial plan inspired by the Rose Main Reading Room in the New York Public Library, in favor of a simpler aesthetic befitting a takeout bakery. Think lots of white tile, a rusted-metal menu board with magnetic letters above the ordering counter and a birdcage chandelier that nods to the Blackbird name, which in turn evokes the Gallows’ logo. And the doughnut-making will be on full display beyond a glass wall.

“It’s not cluttered now. Originally you weren’t going to see the bakery, but then we felt, we’re building such a cool bakery, and the equipment is all brand-new except for one piece,” Gullo says. “You might as well see it.”

There will be eight to 12 kinds of doughnuts available each day, including both cake and raised varieties.  The vanilla glaze and a stack of mini doughnuts (available in threes) will always be on hand, but the rest will change with the season and the kitchen’s whim. Flavors that have struck a chord so far: toffee, Sriracha glaze with sesame seeds, chips and French onion dip (inspired by Yaffe’s obsession with chips and dip), lemon honey pistachio and even sourdough. To start, the shop is expected to be open Thursday through Sunday, from 7 am to mid-afternoon, but the group plans to eventually serve seven days a week, fill wholesale orders and even dabble in mobile projects.

For now, the concept remains simple. Doughnuts and a custom blend of coffee from a local roaster are all that customers will be able to order, but that might not be the case for long.

“Right now, it’s just doughnuts, but we love soft serve,” Gullo says, dropping a hint with a big smile. “I love soft serve. Seth loves soft serve.”

Blackbird Doughnuts 492 Tremont St., Boston (617-482-9000) blackbirddoughnuts.com