MISTRALKITCHEN, THE 2.0 VERSION of William Belickis’s erstwhile Belltown jewel box restaurant Mistral, is one overwhelming enterprise.

Five thousand square feet. Six discrete dining rooms. Two kitchens. Even the extra-wide, extra-thick steel door off Westlake Avenue, located just where downtown gives way to the burgeoning hot zone of South Lake Union, is about the heaviest thing you’ve ever opened before taking sustenance.

So it was unexpected when this overwhelming exterior gave way to an entry, lined with humble bushels of produce, that delivered us straight to Belickis. The boyish toque greeted our anonymous party at the host station with such warm serenity you’d never know that he runs MistralKitchen’s operations, not to say its ovens and stoves, with nary a day off all week. “Actually I haven’t had a day off since November,” he grinned, adding weakly, “Did you know this place is four times the size of Mistral?”

The steely, techno-sleek main room thrummed with stylish professionals in various states of rowdiness (more later on that unlikely state of affairs) and the bar counter was scattered with diners watching the chefs at work in the long open kitchen. Up a few stairs to the right a couple of intimate alcoves—including one with a fireplace—enclosed lively groups enjoying cocktails and noshes. Behind the kitchen to the left, an entirely separate dining room, the cashmere-elegant and aptly named Jewel Box, contained connoisseurs enjoying the kind of multicourse feasts Belickis made his name on at Mistral. No one had booked the $200-a-head Chef’s Table for the evening, but if they had, Belickis would be playing affable host and able chef for that crowd, too.

Full plate. But at the moment Belickis was consumed with chervil. “Aren’t things in the garden weird this year?” he marveled. “My chervil didn’t do a thing all summer, then it just roared in February!”

This horticultural obsession will surprise no one who’s followed Belickis from Mistral. The Belltown temple of Euro cuisine enjoyed acclaim that was at once rapturous and unnaturally quiet, as if devotees wanted to keep their shrine to themselves. Those cultists knew that Belickis was always more interested in growing his own vegetables and herbs on-premise and distilling them into potent gastriques and stocks and foams than he was in playing famous restaurateur. Mistral was exclusive and rarefied; its pleasures culinarily arcane. When he announced plans to open this huge restaurant with multiple eating zones designed by pooh-bah architect Tom Kundig…well, the whole idea sounded a little three-ring-circus for the likes of a guy who was first and foremost—and I say this with all admiration—a food nerd.

Hence the second shocker of the evening: Belickis can do casual.

The main room is all pewter and black and stainless: concrete floor to open ductwork ceiling, with raw-filament bulbs and tall windows and that busy open kitchen in between. And, on our weeknight visit, it was vital as a heartbeat. Urban sophisticates slammed the place, loudly. They may be drawn by the inventive cocktails and an admirably wide-ranging wine list. But I suspect a bigger reason is that Kundig’s forthright design and Belickis’s down-to-earth, affordable menu together deliver a single clear message: You have left the temple.

Make no mistake: The food still bears the imprint of Belickis’s trademark obsession with pure, vegetal essences. A shallow bowl of Manila clams in a briny, buttery sauce was pocked with chorizo and brightened with a sunny orange gremolata. A single sashimi-grade sea scallop, almost creamy, arrived strewn with artichoke hearts and cipollini onions in a chlorophyll-bright herb sauce. Musky beets deepened a fine preparation of daurade whitefish; rarely seen black radishes contributed a fine offsetting bitterness to blush slices of lamb leg with sweet baby carrots.

Such concentration on the purest essence of one’s produce might seem precious in the hands of a lesser chef, but in Belickis’s house it’s always grounded in substance. This I realized in the Jewel Box, which enshrines the Mistral concept (eight courses for $90; four courses for $60; wine extra), only with plusher surroundings in a softly classy palette of oyster and gunmetal. In this hushed white-linen room, the antics on the other side of the wall seem of another restaurant entirely.