There are tweezers in constant motion at River Twice, placing tiny borage sprouts over shaved sunchokes and raw bay scallops, arranging minuscule mushroom caps beside aged duck and Badger flame beets, layering plumes of creamy uni over bowls of heirloom grits.

But then there is also the two-fisted indulgence of a stacked burger whose drippy pink juices are almost too much for its bun to hold. And chef Randy Rucker’s soulful gumbo? Its deep-brown broth is so heady with smoked duck that it whisked me from this South Philly chef’s counter straight back to the Gulf Coast.

There is gastronomic preciousness and there is genuine rustic oomph, two traits that don’t often coexist. But they’re both served in graceful harmony at this intriguing newcomer, strikingly plated on locally made ceramics, and with such well-wrought clarity of flavors, I couldn’t help but wonder: Where did this come from?!

The answer — Houston via Martha’s Vineyard via Wynnewood — takes some unpacking, considering the cross-country journey that led Randy and his wife, Amanda Rucker, to the triangular space beside the Singing Fountain previously occupied by Izumi. But this sophisticated new arrival is definitely a Philly debut worth celebrating.

Rucker, 41, is a known talent in his native Texas, where he was a James Beard nominee for his work at the Rainbow Lodge in Houston, where he was one of the first molecular modernists and a “mercurial” character who co-owned several other restaurants (laid-back manor, Bootsie’s, and Bramble) before leaving for New England with Amanda, then his girlfriend. After a couple years amid the salt ponds and seasonal tides of Martha’s Vineyard and Mystic, Conn., they moved here to be closer to Amanda’s family, including her dad, Larry Highbloom, their business partner at River Twice.

Amanda, 31, who studied at Moore College of Art & Design and Temple University, has transformed Izumi’s once-dark decor into a comforting atelier of earth tones and natural materials. Breathable plaster walls, concrete counters, and blond wood furniture accent the room, whose 37 seats are divided between tables (with hidden flatware drawers) and a chef’s counter that fronts the open kitchen. Another 26 seats are coming outside when weather permits.

The counter, though, offers the best vantage of Rucker and his chefs, who cook to classic Southern rock tunes (“Lord, I was born a ramblin’ man!”) against a colorful backdrop of big pickle jars and meticulously stacked spices. From black yuzu powder to allium ash and dehydrated mitsuba, they lend Rucker’s fluid cuisine layered shades of global flavors, deepened by house-fermented misos, cultured butters, and local heirloom grains. His “no waste” mantra means you’ll taste multiple echoes of ingredients in different guises.

Exotic mushrooms are frequent stars, often pickled or roasted, adding delicate snap to the lush textures of venison tartare and raw seafood. But the trimmed stems also get transformed into an umami-bomb jelly that shines atop ruby tiles of seared tuna set over a sweet-tart mandarinquat emulsion.

Another example: Whole sweet potatoes get juiced for a smoky sauce puddled beneath pork loin with rye berries. But their pulp is dehydrated and powdered into flour that, combined with sweet potato miso, made savory pizzelles that were shaped into remarkable tartlets to cradle Peekytoe crab salad.

Rucker credits prep cook Chris Prewitt with the offbeat pizzelle idea — and it turns out to be a stroke of genius versatility. An earlier take on that crab salad came inside cannoli-shaped pizzelles made from leftover sunchokes, a contrast of sweet sea and earth I found extraordinary. By last week, the tart shells had turned deep purple with Nebula carrots.

The pleasant servers are well-informed but unintrusive — especially for diners sitting at the counter. More will be demanded of them once the beautiful stemware, currently used for BYO wines, benefits from a liquor license expected soon. The restaurant’s unusual name is partly a nod to the many rivers that have highlighted the Ruckers’ landings, including the two that trace Philly, which they’ve described as “the most welcoming city we’ve ever lived in.”

It also pays homage to life’s steady flow of change, as articulated by the Greek philosopher Heraclitus: “No man ever steps in the same river twice, for it’s not the same river and he’s not the same man.”

Randy is the first to admit he was overambitious as a younger chef, with no business sense, a restless impulse to leave restaurants (then regret it), and an infatuation with long tasting menus of highly manipulated food. Some of those techniques are still present at River Twice, where there is, in fact, a seven-course tasting ($85) as well as a la carte options. But he and his cuisine have both evolved to embrace more naturalist elements — foraging, fermentation, and regional flavors — that meld with his personal history in a more mature style that’s beautiful without being overly fussy.

The richness of diced swordfish-belly tartare is elevated by a chili-citrus paste made with yuzu from Bhumi Growers in Bordentown and a finishing spritz of wild orange vinegar. The raw bay scallop dish is all about the candy-sweet New England shellfish, but the snap of sunchokes shingled over top grounds the dish, while the buttermilk broth swirled with vivid green spruce oil convincingly hints at the ranch dressings of his Texas youth.

Cool sea urchin over warm custard is a move Philadelphians have seen before. But River Twice lends it a novel wink of luxury-country fusion, levitating those creamy petals atop Castle Valley Mills Bloody Butcher heirloom grits crowned by the salty Kaluga caviar and butter tanged with shio-koji, a Japanese rice culture.

A similar garnish for the steamed chawanmushi was less successful, the barely-set custard below too light and liquidy to hold the urchin’s weight. It was one of few small misses, along with too many crunchies atop the soft venison tartare and a dull farro pudding for dessert. Try instead the chocolate cremeux mousse drizzled in peanut miso and topped with crumbled smoked cashews.

The chocolate-peanut revamp is a typical move from Rucker, who revels in upscaling downhome dishes. None spoke to me more than the bread dumplings inspired by his mother, Bootsie Pena. They’re shaped from leftover bits of Texas toast sourdough into toothy gnocchi-like bites, then glazed in koji butter and buried beneath a fragrant mountain of shaved truffles. For $15, you can add truffles to the lobster agnolotti, too, but these delicate pasta pouches filled were so good in bisque-y lobster sauce, they hardly needed an upgrade.

The same straightforward satisfaction arrives with the massive 38-ounce hunk of grass-fed, bone-in strip steak, sliced into a beefy fan of thick pink cards. It has a deep swagger from aging in a rub of sake lees and, at $110, was easily enough to share. Then again, I find myself dreaming of the Mother Rucker cheeseburger at least as much, its two glistening quarter-pounders of fat-rich local beef from nearby Primal Supply layered with everything-spiced mayo and pickled onions on a Machine Shop milk bun.

Of course, it’s not on the menu, since Rucker only offers four or five a night. He’s reluctant to give it official status because he fears it might end up being the only thing his guests order. It is that good.

His hesitations are merited, because there so are many other gems worth appreciation on the ever-changing menu: raw Boomamoto oysters sparked with pickled fresh green peppercorns and smoked trout roe; dewy hunks of roasted Maine halibut; seared sea scallops with a brown buttered puree of silky kabocha squash. I encountered different delights at each visit.

Even the cheese course here, which I prefer to the desserts, charts Rucker’s personal history of travels and good taste. One night, a stinky washed-rind beauty of Prufrock came from Grey Barn in Martha’s Vineyard. Another brought a ripe chunk of Camembert-like Thistle from Valley Milkhouse, the Oley Valley creamery that’s become one of the chef’s go-to products in his new home. Is it any coincidence it arrives atop a cushy pillow? Hopefully, that means he and Amanda plan to stick around for a while.