A sigh escaped the line cook’s mouth. Not the harmless self-pitying kind of sigh, but a weighty, ominous heave that betrayed a profound existential dread deep in the man’s soul. Beads of sweat glistened on his forehead. This cook was stressed. Across the kitchen counter, where I was working my way through Roister’s multicourse, $85 prix fixe dinner ($95 on weekends), I prayed that his anguish would not affect the sourdough pancake with marinated mussels he was painstakingly assembling. I was pretty sure those were my mussels, and nothing makes lousier seasoning than existential dread.

At Grant Achatz and Nick Kokonas’s casual three-month-old Fulton Market meteor, which occupies the former Ing space, a giant brick-lined hearth heats the open kitchen. Executive chef Andrew Brochu’s exacting expectations all but traumatize it. I’ve never seen a grimmer bunch of tweezer-wielding worrywarts than Brochu’s kitchen crew, nor felt guiltier that they were on display for my amusement. No one wants to watch an earnest chef get quietly but forcefully berated for some unseen transgression.

While I should’ve been focusing on cerebral comfort food such as buttery-tasting, soy-dusted Yukon Gold fries topped with bonito flakes and served with tofu mayonnaise, instead I was busy mentally cataloging the unsettling scenes that might unfold: a nervous breakdown, heat stroke, a sous chef getting his heart removed with stainless steel tongs. I hadn’t been that edgy since my kid’s last choir concert.

The good news is, this same talented group also cooks for Roister’s rollicking, rustic dining room. Opt for the à la carte meal and you get mostly larger portions of the prix fixe chef’s-counter dishes, but at a table far enough from the kitchen to shield you from any back-of-house angst. Rather than watching stressed-out chefs, you’re guided by playful, blue-jeaned staffers who deliver what Roister’s name promises: fun.

This ostensible emphasis on fun doesn’t mean that Brochu (Alinea, EL Ideas) has abandoned the kind of serious, detail-oriented fare for which Alinea and Next are famous. Here, though, he seems more concerned with delivering pure and simple flavors than with technical wizardry.

A perfect example is Roister’s whole chicken, already a legend. After brining the bird for 24 hours in chamomile sweet tea, Brochu’s team poaches the breasts and sears them in the hearth until the skin caramelizes. The thighs get a buttermilk bath, then a dip in the deep fryer, and the legs and wings get confited and juggled into a chicken salad of sorts, with sunchokes and artichoke hearts. It’s clever, resourceful, and terrific.

The imagination that propels the dishes never feels ego driven or forced. Napa cabbage kimchi is given a tart-sweet dimension with the simple but inspired addition of sweet chili sauce and thin wedges of fire-roasted pineapple. And if I’ve developed a case of scallop crudo fatigue of late, Roister’s bold rendition lifted me from my funk. Plump raw diver scallops are sliced thin and served with morsels of passion fruit, daikon microgreens, and scallops that have been dehydrated, fried, and crumbled to resemble bacon bits—all atop a tangy whole-grain mustard emulsion. Busy but spectacular.

Roister’s Achatz connection carries a certain amount of baggage, to be sure. I’ve been going to Achatz restaurants for more than a decade now, and Roister is the first one that doesn’t rely on brash and mind-bending twists. This kitchen plays it straight, and to great effect. Take the salad of giant grilled asparagus: Slightly charred and draped with thin-sliced fennel and fennel fronds, the crisp-tender spears are dressed with a crumbled macadamia nut vinaigrette to create a deceptively uncomplicated textural masterpiece. The apparent simplicity of the braised pork butt belies the care the kitchen takes with the meat, which is cooked gently for six hours in ginger, lime, molasses, and rum, strewn with crushed peanuts, and nestled in a bed of tender, slow-cooked Sea Island red peas—an Asian-toned homage to cassoulet. The snail-shaped “pipe” pasta, which comes with razor and littleneck clams, limes, mint, and a green chili ragoût, provides similarly pure, unfussy gratification.

This is everyday food from some superior alternate universe.

The menu holds so many cozy treasures it’s easy to overlook some of the more indulgent luxuries. A thick hunk of incredibly tender A5 wagyu beef—A5 being the highest grade of marbling—sparked with togarashi and drizzled with melted butter with sea urchin purée, lands as one of the most stunning steaks in Chicago. And the smoked oysters—each flawless bivalve smothered with preserved galangal and horseradish—are brought out in the skillet they were cooked in, still smoldering and popping alongside wood chips and smoked seaweed.

Occasional clunkers and deviations ambush the menu. A mawkish lasagna with tomato gravy, Burrata, and caramelized onions seems to have wandered in from another restaurant, one where flavors hit you over the head. The D’Artagnan Rohan duck—tantalizing breast meat atop roasted legs—looks like an unashamed, debauched glory. But the tooth-taxing dried oranges and lemons and a mysterious extraneous slab of foie gras make the whole thing feel scattershot.

Overall, though, these misses don’t spoil Roister’s à la carte party. Look around the lively dining room and you’ll witness a level of enthusiasm you’d expect to find at Randolph Street funfests such as Avec or Girl & the Goat. Most everyone looks to be on the second or third cocktail—maybe an impeccable double daiquiri or a carefully balanced Resurrected Panda, which melds mezcal, pisco, lychee, port, raspberry brandy, and lemon. And no one ignores the tiny dessert list, which illustrates a restaurant truth: Do a few things well and people will be happy. Especially if those things are slam dunks like a whipped-honey cake with homemade granola, buffalo milk yogurt, and fresh rhubarb curls or a coy but decadent play on a candy bar made with pretzels, black walnuts, marshmallows, foie gras, and caramel dipped in chocolate.

Reserving a table requires commitment. Roister employs the same online ticketing system as Alinea and Next and charges a $10 to $20 deposit per person for à la carte service, which goes toward your bill. (Prix fixe menus require full prepayment.) And if I haven’t made it clear enough: Book the à la carte meal. You might miss out on a spontaneous creation by the chef, but your experience will be cheaper and far more fun. This kind of exuberant food is conducive to revelry, not solemn voyeurism.

To their credit, Achatz, Kokonas, and Brochu seem to genuinely want their counter jockeys to enjoy what they do. “The restaurant is the kitchen; the kitchen is the restaurant,” boasts Roister’s website. Brochu tells me his cooks are still getting used to the limelight. None of them have worked under conditions this loud or this demanding before. “Some nights are better than others,” he says. “On any given night, there is laughter and excitement from the kitchen, but at the end of the day, it is still a kitchen, and a very serious one.”

I can’t argue with that.