How can something as simple as a Margherita pie, let alone something as elemental as a new restaurant, have such a profound effect? It can when that pizza is miraculously good and that restaurant is the long-awaited Osteria from Marc Vetri, who may be the most important Philadelphia chef of his generation.

Who else could entice people to street-park their Bentleys and Porsche SUVs on this previously drive-by stretch of Broad above Spring Garden? People have long talked about reviving North Broad, but this restaurant, slipped into the ground floor of a massive renovated apartment building, is the first spark of its new life. And they're coming in droves to this bustling urban loft-turned-rustic Italian haven. Its 100-plus wooden seats are packed with that mix of power diners, foodie high society, and chefs on their night off that is the telltale sign of destination-dining buzz.

In this case, a taste of pizza is enough to know that Osteria - the more accessible, and (slightly) less expensive casual sibling of high-end Vetri - is definitely worth the hype.

You can find all kinds of spectacular seasonal pies emerging from the 700-degree heat of the wood-fired brick oven here. There are pizzas topped with snails and fresh spring garlic scapes. There are crusts laced with tender octopus sparked by chile flakes and smoked mozzarella. They come stuffed with white truffled robiola cheese, or scattered with woodsy slivers of snappy bluefoot mushrooms. There is also the Lombarda, which sports homemade cotecchino sausage and a sunny-side-up baked egg.

But it's the Margherita I love. The height of refined simplicity, its crust, sauce and toppings channel such vivid harmony that I'm transported to the pizzeria in Naples where I first encountered this taste.

If you sit at one of the restaurant's four-legged country tables beside the prosciutto slicer or the gleaming vintage espresso maker, or if you catch dusk on the outdoor patio when the stained-glass windows of the neighboring church are aglow, it doesn't require a great leap to imagine yourself somewhere other than North Philadelphia. But it does take a restaurateur with the iconoclastic vision and passion of Marc Vetri to make it a reality.

Vetri's Osteria is, of course, much more than a pizzeria. It is an ode to a wide range of rustic Italian comforts, from homemade salumi and focaccia to inventive pastas and spit-roasted meats cooked over wood fires. There is also a wine list that highlights smart values (almost entirely under $50) and great producers, like Argiolas, Feudi di San Gregorio, and Vietti. True to its name, Osteria is a more familial extension of the lusty, authentic flavors that helped make the 36 seats at Vetri's upscale dining room on Spruce Street one of the nation's most coveted Italian reservations.

Building into the shell of this old warehouse at 640 N. Broad St. allowed Vetri to fully realize his vision for the handsome room. And it is an amazingly warm and evocative space, with sunlight pouring in through industrial windows to illuminate the wine-red-stained concrete floor, the long bar that lines the open kitchen, and a glassed-in wine cellar that looks onto a private room filled with big wooden farmhouse tables. It has the lively bustle of a casual destination - but enough space between tables for comfortable dining.

The service, coordinated by Vetri's business partner and front-house whiz, Jeff Benjamin, is nearly as refined and well-versed as the original restaurant's, although we were obliged to drink a spell at the bar both nights (erg!) before our table was ready.

Once we were seated, though, Osteria chef Jeff Michaud, a former Vetri sous who followed his mentor's path to work in Lombardy for three years, delivered what is easily one of the most compelling Italian menus in town. Virtually everything in the restaurant is made on the premises the proper way.

Among the more amazing antipasti was Michaud's homemade salumi - cotecchino, a coarse-ground sausage scented with Medici spice; creamy testa headcheese; and spit-roasted porchetta, a thinly sliced and herbaceous pork tenderloin wrapped in meltingly fatty strips of belly that came beneath arugula salad and a piquant tonnato puree of tuna and capers.

I'll never look at mozzarella sticks the same way after devouring the crisply fried bread-and-cheese squares of mozzarella in carrozza. But Osteria's starter-course pastas, made from firm semolina, were revelatory.

The unusual gnocchi sardi, more tiny pastas than puffy dumplings, were a shade salty (saltiness also dogged the John Dory tartare). But I found the texture of those grooved little "gnocchi" shells, tossed with peas and crumbled prosciutto in a creamy olive oil sauce, totally addictive. The fusilli with fava beans, pecorino and mint were the pasta essence of spring.

The postage-stamp-sized francobolli ravioli sandwiched a dab of creamy robiola cheese between the most delicate pasta skins and the snap of shaved bluefoot mushrooms.

Entrees evoked some heartier, home-cooked dishes. The soulfully slow-braised rabbit casalinga recipe was taught to Michaud by his Italian wife's grandmother, Anna Carrara, and he replicates it faithfully in the pancetta- and sage-infused white-wine gravy, as well as the polenta that stews in a pot nestled in the wood embers of the pizza oven.

An amazingly tender pork chop from Country Time Farm was an impressive centerpiece for a trattoria classic - a crisply fried pork chop Milanese topped with arugula salad. A thick slice of baby lamb, deboned and rolled around an earthy stuffing of ground-lamb parts, concentrates the intensity of roasted meat and rosemary after two hours on the spit. A $60 price tag seems like a lot for the steak "Fiorentina." But the 32-ounce rib steak is more than enough for two, and the well-marbled prime meat painted my palate with a hauntingly herby garlic savor.

The ricciola (yellowtail) was the only dinner entree I didn't like, as the steam oven left the thick white fish with an unpleasantly flabby, undercooked texture. At lunch, where lively salads, pizzas and elegantly crisped paninis are available, you can also avoid the heavy Taleggio asparagus lasagna, which was bound with béchamel as thick as paste.

Otherwise, my three meals were a dream, down to the sides of crisply fried Roman artichokes and thick, smoky spears of wood-grilled asparagus.

Even dessert brought some unexpected delights, from a gently sweetened polenta pudding topped with hazelnut chocolate gianduja to an array of stunningly silky frozen treats. A creamy coconut gelato tingled with a surprising afterburn of chiles. And sorbetti of blueberry and strawberry were the distilled frozen nectar of the ripest fruit.

Could these be the sorbetti that save North Broad Street? I'll drink a shot glass of perfect espresso to that. Actually, give me another.

Osteria

Excellent

Contact restaurant critic Craig LaBan at 215-854-2682 or claban@phillynews.com.

Read his recent work at http://go.philly.com/craiglaban.