Robert Fathman has opened 11 restaurants in his career, but he’s never experienced anything quite like what’s gone into opening Bel Ari.

After Mark Tosi and Anthony Botta bought Sorriso from Ian Just in January, the restaurant stayed open while Fathman began to change the menu. Then came some tinkering to service before the physical overhaul began in July. The Leather District spot has stayed open during most of the renovations, and now it’s slated to officially open under the Bel Ari moniker on Sept. 10.

“It’s a business and our goal was not to have to shut down for any length of time,” says Fathman, the executive chef at Bel Ari and neighborhood sibling Les Zygomates. “It allowed us to share the experience of our renovation with our customers.”

Sorriso’s customers have been getting a hint of what the Bel Ari menu will look like. The portions have been scaled back, but the flavors have been enhanced, with Fathman at the helm of a kitchen that’s primarily whipping up modern and classic Italian cuisine at prices mostly under $30. Dishes such as pan-seared scallops with squash puree, pancetta, onions and truffle share space on the menu with spinach pizza and a bevy of handmade pastas. Fathman also names some standout sfizi (bar snacks): lamb meatballs with goat cheese, roasted shishito peppers with olive oil, and whipped ricotta with honey and pistachios.

At the bar, Karen Small is using many of the kitchen’s ingredients to carve out the cocktail list. A touch of microbasil inspired her to make her version of a basilico (gin, fresh-squeezed grapefruit juice, ginger beer, simple syrup and basil muddled with burnt sugar). “I want to make sure it accentuates the flavors,” Small says. “I don’t want to have a syrupy, girly drink with bronzino.”

The revamped menu accompanies changes to the restaurant’s ambience. A glass communal table now graces the front window, while large maroon banquettes line the wall leading to the back dining area. The walls—previously adorned by a mural—are now eggshell-colored and decked with works from local artist Janice Eve Dale. New tabletops and light fixtures will help contemporize the space, Fathman says.

“It’s kind of neat. Every night, the trades come in and do a little something else,” he says. “One day they’ll tear out the wine rack and redo the wall, or put in a new hostess desk or a new table. We closed for a weekend, and they painted the ceiling and went all the way down to the floor.”

Aside from keeping up with the busy lunch crowd, Fathman sees another advantage to the “rolling renovation,” which he plans to also oversee at Les Zygomates shortly after Bel Ari opens. It allows for continuity with the staff.

“Nobody has to take any time off. The people in the kitchen are all hardworking guys, and if we closed down for a bunch of weeks, they’re not in the position to hang around,” Fathman says. And he knows the entire staff will be in the right spot when it comes time for the official changeover: “We’re going to be standing ready for a stampede of people going through that door.”

Bel Ari 107 South St., Boston (617-259-1560) belariboston.com