"I'm so sorry to have to rush you!"

This was the last thing we expected to hear from our server at a meal that, any minute, would pass the three-hour mark.

But dinner at Avance is a long story. Everything about this important new restaurant - from its bid to replace the iconic Le Bec-Fin and restore Philly fine dining to modern relevance, to the house barista's tasting notes while delivering our pot of decaf ("you'll get baker's chocolate, caramel and nuts, then different flavors as the coffee begins to cool") - requires something of an epic breath.

That may be a gasp when Philadelphians first glance at the new dining room, which has finally been disrobed of Le Bec's King Louis glitz and chandeliers - inevitable and necessary for this project to have a chance at fresh life. The long, tall box of a room, though, has gone to the opposite extreme, outfitted with such minimalist gray tones, bare walnut tables, dangling Edison bulbs, and tangles of wall vines that it has the soul-sucking effect of a hotel lobby.

You'll still need deep pockets, with dinner easily ranging from $100 to $200-plus per person, depending on your appetite and thirst for triple-markup wines. And many don't blink at the bottle prices: the sweet spot for business diners has been $165 to $225, says sommelier Alexandra Cherniavsky. That's no shocker given the gastronomic history of this Walnut Street address. And Avance is hardly the only place in town tackling pricey multi-course tastings.

But the steep cost raises expectations for a complete fine-dining experience - and puts its flaws under a microscope, a fitting lens through which to view precious plates constructed by tweezer-wielding chefs. There's no questioning the intricate beauty of the compositions, edible modern still lifes dotted with colorful gel sauces, flower petals, foamy whey emulsions, and powdery drifts of frozen cardamom-yogurt "snow." And there were many moments when Roxborough native chef-partner Justin Bogle's talent was clear. Like those hollowed-out eggshells filled with silky custard concealing beads of hackleback caviar and bacon-flavored tapioca, a signature from his days as a two-star Michelin chef at Gilt in New York. But shortcomings at his ambitious Philly debut, funded by two unnamed partners (plus Chris Scarduzio), were surprisingly prevalent in both the kitchen and dining room.

And they increased as each of my three meals ratcheted up in complexity. A simple first meal primed my hopes in the downstairs bar, which has all the intimacy and energy the upstairs lacks. I enjoyed the cocktail wizardry of Bradford Lawrence and a memorable lamb burger with smoky red-onion marmalade and chickpea fries.

My first dinner in the upstairs dining room, though, a traditional three-course a la carte, began to reveal concerns. The dreaded waiter welcome spiel was exhausting, a seemingly interminable recitation of every menu item that reminded me, ironically, of Le Bec's stuffier days when waiters did the same in French. We enjoyed a fine Selbach-Oster Riesling Spätlese - at $23 (!) a glass. A strange soundtrack, all the while, chimed through the room like bad Vegas lounge music.

There were several highlights, like an earthy tumble of sweet Jerusalem artichokes with sunflower-seed brittle and pears. A thick hunk of moist swordfish in yeasty chicken broth was topped with a clever ramen-like nest of crispy chicken-skin threads. A surprisingly rustic and tender pork neck over rice porridge grits was hands-down my favorite plate, its meaty savor heightened by the subtle surprise of briny razor clams and seaweed.

The truffled crust on the striped bass, though, lacked intensity. The steamed chawanmushi egg custard was too shallow and stiff. The arctic char tartare was gorgeous, but overwhelmed by the tartness of the "anti-griddle"-frozen green disc of apple-fennel juice. And the desserts, lowlighted by a caramel-glazed sphere of dry cake and an aerated buttermilk parfait that looked and tasted like a sponge, were simply disasters.

When we stepped up for the full $138 chef's tasting two weeks later, though, Avance wasn't yet ready for its training wheels to come off. The excellent house-baked breads (smoked wheatberry, Armenian rye) became a tasting of one cold roll after another (save for scorched brioche with the foie gras.) Servers hovered, popping over to answer eavesdropped questions that hadn't actually been asked. Cherniavsky's by-the-glass pairings were mixed, scoring with a fleshy Greco from Basilicata to start, an Angerer Grüner for the tartare, and a Florido Moscatel sherry for the custardy frozen foie gras, but stumbling over reds, with an $18 just-opened 2001 Crozes-Hermitage that needed more time to open up and a funky South African cab franc blend that was just off.

It was disappointing that many of my eight courses were taken from the standard a la carte menu, much of which I'd already eaten two weeks earlier. Plus, the second renditions were worse: the crispy-skinned duck breast was lukewarm; the chawanmushi custard was topped with chewy, half-crisped barley that lodged in my teeth. My guest's vegetarian menu was in many cases just a version of my plates minus the proteins - the potato puffs without silky chicken mousse, the eggs with no caviar pop.

Of course, Bogle can perform serious veggie acrobatics - the kind of technical jujitsu required to sell a $25 entree essentially built around a stalk of broccoli. The dish, "Brassicas," employs no fewer than nine involved techniques, from sous-vide poaching (in broccoli stock) and grilling over Japanese charcoal, to smoking cabbage for creamy puree, pickling mustard seeds and dehydrating cabbage leaves into chips. It's a shame the stalks were so soft by the end of their labors (not unlike the less-than-snappy seaweed-roasted baby carrots with nasturtium vinegar.) It's also a bummer that the chips were inedibly salty. But mostly, I'm still chuckling at our server's insistence they were actually tiny Brussels sprouts the cooks had rolled out into larger leaves. She was incorrect about that, among other details.

It's a good thing, at least, that I like beets. They appeared throughout my tasting - juiced, powdered, and dehydrated into "raisins," with cameos alongside the sturgeon (which had a murky aftertaste) and even in our desserts. It worked better with the rhubarb and roasted rice ice cream than it did as sorbet for chocolate cake. But both were preferable to the soggy-crusted mini-pastries that arrived almost simultaneously with the lumberjack-bearded barista.

I applaud Avance for teaming with Elixr for serious coffee. But who's going to drink a fresh pot of Chemex brew at 10:30 p.m.? We opted for decaf and asked for the check, which seemed to startle our server though she'd known my guest had a train to catch.

I only wish that I'd wanted to linger - and that Avance was the answer to the future of this legendary gastronomic address. But - after one last epic breath - we couldn't leave fast enough.


Justin Bogle discusses Avance at www.inquirer.com/labanreviews. Inquirer restaurant critic Craig LaBan hosts an online chat at 2 p.m. Tuesdays at www.inquirer.com/labanchats.