[ review ]

If you want to know what kind of restaurant Square Peg is, you need only look at the numbers. In six weeks of business, the Cuba Libre crew’s neo-diner in the old Marathon Grill spot has sold 1,700 mac ‘n’ cheese grilled cheeses. That’s about 40 orders a day.

“I’ve created home-run dishes in my life, but none has been as popular as this grilled cheese,” says the sandwich’s sire, Square Peg chef Matthew Levin. “The foodie community and people I know are all, like, ‘What happened to him?'”

Bills would be my guess. A mortgage, maybe? Chefs, just like plumbers and teachers and writers and everyone else in the 99 percent, need paychecks, and after parting ways with his partners at Adsum last summer, Levin was a chef without a kitchen. He was doing some consulting and small-scale corporate catering, unfulfilling gigs for anyone with Levin’s unruly brand of creativity, when old buddies Larry Cohen, Barry Gutin and Bob Gallo (who hired Levin as the chef of Jersey’s Pluckemin Inn about eight years ago) came calling. They needed a chef for a new project at 10th and Walnut. The rest is mac ‘n’ cheese-stuffed history.

“The name fits me,” Levin says. “I’m definitely a fucking square peg trying to fit in a round hole for a while now.”

I think it’s a terrible, unappetizing name — the logo’s askew, Scrabble-tile “P” in particular irks my soul — but if it resonates with Levin, more power to him. The 36-year-old has definitely had his share of imperfect fits: the diamond shackles of Lacroix; Masano and Rubb, the restaurants that never came to be; and even Adsum, his deep-fried pride and joy. But after visiting Square Peg and partaking in Levin’s latest culinary efforts, I’m not convinced this dimly lit, bilevel brick den is the square hole he’s been seeking. There would be more finesse in the cooking if it were.

Take the Jewish wedding soup. It’s a sly cultural combo that could be born only of Levin’s brain: matzo balls, chicken meatballs, parsnips, carrots, turnips and lacy leaves of braised escarole adrift in a bowl of dill-kissed chicken broth. I loved it on sight. But what good is a brilliant idea when the executed vision is a hot mess? The broth looked the part, its surface shimmering with the golden droplets of fat prized by bubbes all along the Eastern seaboard, but the flavor was weak, a mere innuendo of chicken complemented by a lack of salt. The matzo balls were more like matzo boulders. I spooned my way to disappointment while Levin watched the Flyers at the bar.

The soup could have borrowed some salinity from the too-salty fried calamari, which came with hacked-up long hots, pastel shrimp crackers (hard to eat with the crusty squid) and a smoked honey aioli. Wavy egg noodles buried in short-rib stroganoff, the plat du jour, could have also used salt, not to mention acid and fresh herbs to balance the dish’s tiresome richness. A scattering of pumpernickel crumbs provided texture, but the leaden gravy did its best to swallow up the notes of cocoa and caraway.

The aggressive deep-fryer was no friend to crème-brûlée-battered brioche French toast “pegs” from the all-day breakfast menu. Beneath flows of rummy bananas Foster and burned coffee caramel, the toast alternated between unpleasantly bitter and unflinchingly sweet. Can a brother get a berry?

Perhaps worse than the poor execution, these plates were dull, with none of the verve typically associated with Levin’s cooking. Say what you will about Tastykake sliders and Four Loko prix-fixes, at least they were something to talk about. Square Peg’s offerings, mostly, are something to yawn about.

Levin knows this. He’s the first to admit Square Peg’s concept (and eventual plans to expand nationwide) come at a price. “Obviously there are concessions,” he says. “[The food] had to be a little bit more down the middle of the road. Super poutine doesn’t work at a fucking strip mall in Atlanta. Mac ‘n’ cheese grilled cheese does.”

So does that make him a sellout? Not so fast. Square Peg’s ownership has granted enough culinary leeway that the menu, no matter how mass appeal, still feels like a Levin production. (Wink-winks include General Tso chicken cobb salad and cheesesteak pot pie.) And there are glimmers of his talent for upscaling everyman grub, if you know where to look. The wings are a good place to start, done here with a fiery, faintly sweet white-chocolate ganache steeped with habañeros, fennel seed and star anise, a fresh take on an old Lacroix recipe.

“Late Night” turkey sliders are served the way Levin eats them on Thanksgiving evening, cold from the fridge, to some controversy. But I liked how the chilled components (sliced brined turkey breast, vivid cranberry relish, sage-scented stuffing, marshmallowy sweet-potato casserole) contrasted with the warm turkey gravy dripping from the mini snowflake buns. And it’s hard to complain about soft-serve suffused with the childhood essence of peanut-butter Cap’n Crunch.

Then again, aren’t we getting a bit old for that? I can eat bad-for-you cereal with the best of ’em, but doing so at restaurants lost its naughty thrill a minute ago. For a long time Levin held the front line of Philadelphia’s fun new food ideas; now it feels like he’s telling the same old jokes.

Which brings us back to the question people are asking: “What happened to him?”

Well, he just put a “Foie Gras Double Down” on the menu. “Guess what? I’m BACK people!” Levin joked on Twitter. But for how long this time?

(adam.erace@citypaper.net) (@adamerace)

Square Peg | 929 Walnut St., 215-413-3600, squarepegrestaurant.com. Lunch served Mon.-Fri., 11 a.m.-3 p.m.; dinner served Sun., 3-10 p.m.; Mon.-Thu., 3-11 p.m.; Fri.-Sat., 3 p.m.-midnight. Brunch served Sat.-Sun., 10 a.m.-3 p.m. Appetizers, $4-$14; entrées, $14-$23; desserts, $7.