Mamma Mia: The Old World comes to D.C.

When is a wine glass more than just a wine glass?

When it comes in two sizes: a long-stemmed flute for bottle service, and a short but curvaceous tumbler for one-glass orders.

“That’s how they do it in Italy,” the server explained to me as she poured a generous helping of sweet, aromatic valpolicella. That’s also how they do it at Potenza, the sprawling restaurant from former Zola chef Bryan Moscatello that is luring patrons to McPherson Square.

Potenza’s charms are multifarious, beginning with its in-house bakery and recession-friendly panini for breakfast and lunch, in addition to the dinner lineup. But it is the authentic details that make the kitchen sing — from the two types of wine glasses to the selection of cold, cured vegetables to the “Sunday gravy” sauce that tastes like it came straight from the Sopranos’ kitchen. Other restaurants serve Italian food, but Potenza serves Italian food in the Italian style.

And although there is a southern Italian province named Potenza, some of its namesake’s best dishes actually hail from the north. An appetizer of palm-sized baccala fritters, mimicking a popular Milanese salt-cod recipe, bursts into a bloom of peppery velvet on the tongue. The fish’s natural grease is not swaddled by excessive breadcrumbs, the cardinal sin of most fritters, but balanced by the fresh snap of a light parsley aioli.

The wild boar ragu, a typical Tuscan recipe, is another northern Italian standout on the menu. Its wine-based sauce has the heft of a winter stew, hiding gems of juicy Portobello mushrooms between each bite of tender meat. While the ragu drowns out much of the flavor in the accompanying peppercorn pappardelle, made fresh in-house, the entree survives the loss.

Potenza is not filling an obvious niche in the District, where Obelisk, Locanda and Palena already demonstrate exemplary Italian cooking night after night. But its quintessentially Italian style makes an unexpectedly good match for downtown’s buttoned-up locals and tourists.

The dark-wood-paneled bar area, with silently spooling TVs and Peroni beer on tap, gives the K Street crowd a more refined alternative to the sports bar and steakhouse circuit. Office-dwellers, meanwhile, have started hiking up for an espresso at Potenza’s pastry counter rather than waiting for their umpteenth Starbucks. Servers are not always timely, no matter what hour you visit, but their winning patter — one waiter got a laugh by asking his table for hairstyling advice — is reminiscent of the Italian insistence that a good meal makes you forget the time.

Tackling Potenza’s expansive menu is easier if you come hungry and ready to experiment. The portions can vary from belt-busting to slim, depending on the dish, and the appetizers are ideal for sharing by groups. A plate of succulent lamb polpettine, the small meatballs commonly served in central Italy’s Abruzzo region, owes a flavor debt to the superb lamb sliders at Zola, which shares a chef and owners’ group with Potenza. But be warned that you may fill up quickly on the lamb’s piquant red pepper sauce, which cries out for a soaking from the fresh focaccia bread that arrives quickly at each table.

That bread, along with slim, crunchy grissini breadsticks, is almost impossible to resist dipping. Between the polpettine sauce, the dense provolone-cheese bath that matches up with fried risotto balls and the garlicky, tomato-flecked broth that carries a snow-white bowl of mussels, it’s easy to finish the appetizers with an uncomfortably full stomach. (The fried calamari, which wilts in the face of too much breading and a bland “spicy puttanesca” sauce, is the only choice that leaves you hungry after the first course.)

But over-indulging in small plates could hamper the appeal of Moscatello’s pastas, all of them almost comically rich but several delightfully inventive. The best bets are the wild boar ragu and the spinach gnocchi, served in a gorgonzola cream sauce that manages to maintain subtlety thanks to a generous addition of garlic and walnuts.

The aforementioned “Sunday gravy” is an Italian mamma’s hefty specialty, pairing mercifully few fat rigatoni with four kinds of meat: oregano-flecked brasciole beef, fennel sausage, meatballs and spare ribs. The Sunday sauce is conceived to simmer on the stove all day, with a dollop of fresh ricotta cheese melting on top, but Potenza cedes an advantage by not serving its version piping hot. Still, anyone with a hearty appetite will find much to love in the dish.

The fish and meat courses are smaller but worthy of notice, particularly a poached monkfish whose flaky texture tangos well with smooth sautéed potatoes and olives. Pizzas are fired in a 6,000-pound brick oven that sits behind glass in the back of the vast dining room. Their almost wafer-thin crusts are dotted with just the right amount of black char, but rarely enough cheese to make a full impression on the palate.

Potenza’s embrace of Old World style comes full circle with its desserts. All the classics are on order, from tiramisu to sugar-coated bombolini donuts to fruity, icy lemon sorbet. As overpowered as you’re likely to be by the menu’s robust flavors and decadent dressings, make sure to order dessert — even if you take it to go. That’s how they do it in Italy, after all.