For the Yardley old-timers who've known this riverside luncheonette for nearly four decades as Charcoal Steaks n' Things, a go-to diner for pit-grilled burgers, turkey clubs, and Western omelets, the breakfast and lunch menus are still "safe."

After all, owner Anton "Tony" Plescha, who took two years to rebuild this institution (now elevated 10 feet above ground) after a devastating Delaware River flood in 2006, still happily mans the a.m. griddle.

But when the dinner hour arrives and Plescha's executive-chef sons, Mark, 28, and Eric, 26, take over, the BYOB now known simply as Charcoal morphs into a kitchen of ultramodern ambition heretofore unexpected in this quaint Bucks County borough. Vacuum-sealed meats in plastic bags emerge from four-day baths in the immersion circulator. Peanut butter gets turned to powder. Popcorn is liquefied into sauce. And the chilling mists of liquid nitro drift across the dining room from bowls of made-to-order guava and blood orange sorbet.

"They're doing things radical and modern," concedes Papa Plescha. "We're trying to get a new clientele in here and keep on growing."

So instead of pot pies, there are pork bellies. There's peas and carrots, too, but the peas are Vita-Prepped into a buttery green froth that pools around a tender lamb shank, and those carrots, crisscrossed batons that look like works of root veggie art, were airlifted from a fancy Ohio farm for $120 a five-pound case.

The inspirational quote on the blackboard menu is not from Escoffier (or even Fanny Farmer), but the fictional Daniel Faraday from Lost: "It is not enough to know the principles. What one needs to know is how to manipulate them."

Manipulation, tweaks, and oblique references are the cornerstones on which Mark, 28, and Eric, 26, have built their irrepressible menu, channeling the wit and techniques of cookbook idols like Thomas Keller and Ferran Adrià, and tweeting kernels of gastro-science wisdom from local stars like Adsum's Matt Levin.

If their fried chicken looked awfully similar to Adsum's - cooked sous-vide in buttermilk, fried in high-tech Crisp Film starch - it's at least a partial result of their Twitter exchange. But if imitation is the sincerest form of flattery, then Yardley-ites should be grateful their striving cooks are at least flattering the right chefs. Their apple-smoked, brown-butter-basted Pillsbury biscuit is a wonderfully original touch to what must surely be the crispiest fried chicken that side of Sesame Place.

"People come in and dine for two hours now, when before it was 40 minutes," said Tony Plescha. "Instead of $10 dinners, we're doing $13 to $30, and no one has complained yet."

The pleasant young waitresses have safeguarded a folksy warmth that would be equally at home serving blue plate meat loaf specials. (And despite its bucolic river view, the newly rebuilt dining room remains true to its frumpy coffee shop DNA.) And yet, those servers nimbly convey every ingredient and technique with a genuine enthusiasm for the kitchen's food-science fantasies.

And when the brothers are in the groove, they can pull off some genuinely stunning plates. Their twist on "Oreos and milk," for example, brought gingersnap cookies sandwiched around decadently creamy stuffings of foie gras, set over crumbled shards of frozen sweet milk. It was a startling collage of textures, spice, and temperatures that evolved as I ate, the frozen milk melting back into a familiar puddle of cookie-dipping dairy comfort. A dish inspired by A&W burgers and root beer floats produced a short rib I'll long remember - brined in sassafras, anise, and juniper, then slow-cooked sous-vide for so long (four days at 127 degrees), the savory meat was medium-rare-pink yet pull-apart fork-tender.

As with many young cooks, though, there were numerous experimental hiccups. Their quest for a novel presentation of pork belly – curled like a pancetta coil – harbored so much unrendered fat, no one at our table wanted a second bite. The seemingly random addition of powdered peanut butter and a pear puree that looked like baby food made a bad idea worse.

Too many dishes suffered from concept overdrive. Had the menu not informed me the scallops with orange-scented risotto were meant to evoke "bbq" I wouldn't have been disappointed by the lack of smoky pit-master oomph. The squash soup topped with a marshmallowy pouf of whipped almond methylcellulose tea (a nod to hot cocoa) would have worked if it hadn't been over-spiced with cinnamon. A vinaigrette with huckleberries had a delightful flavor, but its purple hue made the greens look dirty.

It remains to be seen whether these gaga-for-gizmo cooks can get their point across consistently without the crutch of surefire sous-vide, especially with delicate seafood. An overcooked striped bass negated the cleverness of buttered popcorn pureed to a sauce for fish, alongside black pepper risotto, an idea drawn equally from Peruvian ceviche and movie snacks.

Their hands were more steady with the seared skate, glossed in hazelnut brown butter and crispy chickpeas. The escargots were wonderfully tender in a vivid green pond of herbed garlic butter that I could drink through a straw. And a pan-seared lobster cake, butter-basted with thyme and served over a saffron aioli, offered a satisfying twist to Anton's classic crab recipe.

There were other comfort tweaks – all involving duck – worth noting, from the superb mac 'n' cheese topped with a leg of confit to those snappy little "quesadillas," whose crispy tortilla rounds sandwiched Charcoal's creamy rillettes, with veggie salsa and hot pepper Cabot cheese.

The "Charcoal burger" gets a trendy makeover with a sunnyside-up egg, a brioche bun and house-pickled onion relish on the bottom. But the taste of the Angus patty – perfectly pink and perfumed with a campfire whiff of smoky coals – evoked deep nostalgia from my tablemate, an old Charcoal Steaks vet who used to treat his best employees to the occasional burger perk.

Given all the tricked-out traditions, I kept waiting for something alarming to pop out of my French onion soup like a Jack in the Box.

Alas, it was an unreconstructed diner bowl of onion broth with a molten lid of oddly chewy cheese. I wondered why they even bothered.

Perhaps as homage to Charcoal's homey luncheonette roots? The unadorned Formica tables and no-frills room may also be the result of that same back-to-the-coffee- shop impulse – though just a little effort on the decor for the nighttime crowd doesn't have to equal pretense. The brothers' culinary adventures certainly merit a more sophisticated setting, if only for the evenings.

After all, it's only a few daring hours each night before the sous-vide bags once again plunge into their baths for the slow cook and the clouds of frozen nitro are sealed up. Then Papa Plescha comes back for the morning service, turning Charcoal's old-school omelet griddle back on to "safe" once again.

Next Sunday, Craig LaBan reviews Catahoula in Queen Village. Contact him at 215-854-2682 or claban@phillynews.com.