Like the plaintive fado ballads sung by Mariza that tumble through the garlic-scented air and candlelit alcoves of KooZeeDoo, the flavors at this Northern Liberties BYOB exude the unabashed zest of pure Portuguese soul.

Fizzy vinho verde wine steeped with bay leaves and bell peppers adds swagger and snap to sublimely tender chunks of braised Berkshire pork that mingle with tiny cockles and briny littleneck clams. The liquid smoke of crisply rendered chouriço brings an earthy shine and crunch to the "duck rice," a terra-cotta crock brimming with rice enriched by duck stock and giblets topped with a rosy seared breast. And plump sardines, lightly grilled and vibrant with their distinctive marine tang, pose with roasted peppers over slices of rustic cornmeal broa bread like silvery emissaries of the Algarve coast.

That fabulously earthy broa, also served warm to start the meal with an addictive dish of pickled ivory tremoços beans (lupinis peeled and eaten like edamame), is baked in house by co-owner Carla Gonçalves, whose childhood and family in northern Portugal inform the genuine spirit of this unusual endeavor.

The more celebrated cuisine of neighboring Spain, of course, has been well explored from every tapas angle. But this is the first kitchen I've experienced in the States to elevate the authentic flavors of Portugal to another level. Some dishes might be familiar to those who have explored the pork-and-clam pots of the Portuguese cantinas in Northeast Philly and Riverside.

But Gonçalves' husband and partner, chef David Gilberg, 30, who did decent enough work in previous posts at the Ugly American and the opening of Coquette, has clearly stepped up his game to a higher level of inspiration. An apt comparison, perhaps, is what Konstantinos Pitsillides has done for traditional Cypriot flavors at Kanella.

At KooZeeDoo (the phonetic spelling of cozido, which means "cooked" in Portuguese) Gilberg and Gonçalves have a like-minded approach, an embrace of rustic food so convincing, they've managed to turn chicken gizzards - milk-soaked then braised with wine and a garlicky "refogado" base into tender dark-meat nuggets - into an unlikely best-seller.

The Northern Liberties setting, in the rambling exposed brick space once occupied by Copper Bistro and Aden, has the simple-but-satisfying warmth of a classic Philly BYOB. Votives flicker in wall nooks behind frosted frames. Young servers deliver food from the open kitchen with informed enthusiasm minus the pretense. And there are just enough flourishes here - the folkie fado sound track, the cork-topped tables, the "Gallo de Barcelos" rooster painted for good luck on the wall - to tastefully signal the theme.

In the kitchen, meanwhile, Gilberg taps Portugal's powerful peasant flavors, rather than a more superficial fusion approach, and simply updates them with better ingredients, seasonality, good technique, and more sophisticated presentations.

The masterful caldo verde soup, for example, is inspired directly by the home cooking of Carla's mother, Delila, but the silky potato broth is artfully threaded with green collard ribbons and a button-down floating row of cuminy chouriço rounds on top. Raw goat's milk from Lancaster is transformed into a firm and crumbly fresh cheese served between a sweet side of tomato jam with rosemary honey and a savory pool of Portuguese olive oil and sea salt on the other.

The rabbit is also local, and stewed "hunter-style" to such a vivid savor, I can still smell the puff of steam that escaped when the crock's lid was lifted tableside. It smelled of bay and wine-steeped smoked bacon. And the sublimely tender meat inside tangled with earthy twists of black trumpet mushrooms, snappy green favas, and crunchy brussels sprouts.

That dish, like all the entrees here, are served in family-style portions, the humble Iberian neighbor's hearty reply to Spain's precious tapas. The deep crock of bacalhau is so intense, for example, the milky flaked salt cod mashed with rich potatoes, olive oil, and hard-boiled eggs, you'll want to share. Likewise for that rich duck rice.

Many of them arrive in the canoelike hollow of an upturned terra-cotta roof tile. The seafood feijoada, for example, is juicy enough to need it - its buttery, brothy white beans brimming paella-style with a bounty of perfectly cooked lobster knuckles, clams, shrimp, sepia, and octopus. The "cozido minhoto," a sort of Portuguese take on pot au feu, brought a country butcher's medley of rustic boiled meats, with a bony starburst slice of braised oxtail and chunks of morcela, chouriço, and farinheira (sausage made from rendered pork fat and flour) mingling with tiny root vegetables and wilted cabbage.

While KooZeeDoo certainly leans toward hard-core rustic flavors that aren't for everyone (like the appetizer of crispy blood sausage over a salad of bleeding beets), there are plenty of more accessible dishes, too. The pan-roasted picanha (rump cover steak) is a meat-and-potato lover's dream, and not only because this marinated slab has an intensely beef savor (with a side of prosciutto and sunny-side eggs). The cottage fry-like potatoes may be the crispiest spuds in the city.

I didn't love the shrimp Piri Piri, if only because the gravy didn't have quite the volume of malagueta chili spice I'd expect from such a famously hot dish. The kitchen's various fried "rissóis" turnovers, though, were universal crowd pleasers, the crispy half moons filled with creamy centers of mushroom, shrimp, sweet potato, or tuna.

Gilberg has also created a handful of vegetarian-friendly options, which are a rarity in meat-centric Portugal. The chopped vegetable salad was a refreshing study in cold-weather textures, a crunchy chorus of roasted beets, favas, green beans, shaved radishes, and cauliflower florets snapping in a bright coriander vinaigrette. The milho frito brought a hearty entree of polenta-like fried corn porridge squares over a green puree of favas, cilantro, and mint. And the pureed squash and chestnut soup could have been a vegetarian delight, too, minus the surprising farinheira "croutons" made of pork fat and flour. The cinnamon-scented puree was also so naturally sweet (before the squash was recently replaced with carrot), it might have made a nice dessert.

But of course, Gonçalves' house-baked sweets should not be missed. Her moist shredded coconut tart, bound with yolk-enriched syrup, is one of the richest coconut desserts around. The chocolate "salami" (ganache rolled with crushed cookies into a tube then sliced) comes with cinnamon whipped cream and chestnut-stuffed, chocolate-dipped figs that are worth a dessert on their own. My favorite, though, was the baked heirloom apple special. Topped with a bubbly crown of caramel and hazelnuts over a lemony baked custard, it was just the kind of gem that blurs the line between restaurant and home cooking, with a simple look of rustic comfort, but a refined intensity that makes an impression on the paying public.

It's a rare and delicate balance indeed, not unlike a powerful fado folk ballad. But KooZeeDoo hits those notes with a soulful touch that is satisfying from start to finish.