By Paul Reidinger

IF YOU WERE to cast James Ormsby in a Shakespeare play, you would be sure to give him a part in which he could wield a rapier – as Tybalt or Mercutio in Romeo and Juliet, say. He has the racy, slightly pugilistic look of a stylish fencer (he would also be a fabulous Rhett Butler, with apologies to the sadly miscast Clark Gable), and as he moves about the elaborately pillared and quilted dining room of his new gig, Jack Falstaff, he seems most ... un-Falstaffian. Falstaff, as you surely will remember from your college readings of Henry IV, Part II, was jolly and fat; Ormsby is linebacker big but as sleek as a panther. But then, Ormsby has become a devotee of slow food, and Jack Falstaff's menu reflects this emerging ethic, which attempts with considerable success to reconcile the pleasures of the table with the health of the earth and of ourselves.

Would Falstaff have had any truck with such a noble undertaking? He was an inveterate carouser, so no, almost surely. But while Jack Falstaff might serve a menu emphasizing the organic, the seasonal, the local, the slow-cooked – a virtuous menu – the place does have its own sort of vivaciousness. The restaurant belongs to the PlumpJack Group, after all, one of whose principals is Gavin Newsom, a onetime high school baseball star and present-day politician of some nerve who has proved he's no stick-in-the-mud, even if we eventually learn he does indeed sleep in those dark suits.

Those with long memories for short-lived restaurants may recall that Jack Falstaff's predecessor at its SoMa address was a place called Two B, which survived for literally a matter of a few days in the fall of 2003, like one of those strange fish that live, breed, and die in brief desert puddles. But PlumpJack restaurants are notable not least for their longevity, beginning with the 11-year-old mother ship, PlumpJack Café, where Ormsby most recently cooked for a number of years as a worthy successor to Maria Helm.

Although the name Jack Falstaff suggests a hearty British pubbiness accented with the smells of fish-and-chips and bangers and mash, the new place in fact shares with PlumpJack a hushed, voluptuous energy. It is a big space full of smaller ones, from the heated, enclosed patio to the tables along the southwest wall, concealed from the rest of the dining room by huge pillars and sage green velour drapes. The walls are extensively lined with sound baffling in a giant quilt pattern, which is not only striking visually – it is like being seated inside a giant jewelry box – but helps control the noise. Jack Falstaff is lively, nearly Falstaffian in its good cheer, you might say, and at the same time it's an easy place for two people to have a conversation in.

"It's really an updated supper club," my dinner companion noted in a normal tone of voice from across the table. Yes: jazzy music (audible, not overwhelming), lots of spot lighting, a certain speakeasy mood. We were nibbling at two small dishes of Jack's Snacks ($2 each) – spicy crisped chickpeas and spicy flash-fried sage leaves; there are several others – which nicely augment the fresh bread and the sizable cocktail list. While the snacks are cheap, the cocktails are a not-inconsequential $10 each, which amounts to giving notice that Ormsby's slow food is going to cost you. After four years of flat or declining restaurant prices, the Jack Falstaff tariff card indicates that the ticker is headed upward once again.

Ormsby has cooked at some rather grand places over the years (including Aqua and the haute-whimsical Flying Saucer), but his basic instincts in the kitchen seem to be vernacular. He turns out pastas, or pasta-like dishes, that would do many an Italian restaurant proud, and at the same time he deftly steers away from such perils as white flour, using farro spaghetti ($18), say, or fettuce-like ribbons of zucchini ($10). The former might be tossed with a sauce of green beans, pine nuts, and currants, while the latter could end up dressed with a zestier combination of chili flakes, sage, mint, pine nuts, little lamb meatballs, and a good grating of grana padano cheese.

The theme of slowness finds explicit expression in the turkey sandwich ($11), made with slow-roasted Diestel breast meat and rolled in flat bread with bacon, sweet peppers, and aioli. The Kennebec fries on the side fell to the prosaic side of sublime, but we polished them off anyway. And a related theme is the reinvention of familiar dishes, including the chipotle-dusted house-made potato chips accompanying big-eye tuna seviche ($10), in a bath of coconut milk and lime juice, a Thai-style papaya salad ($12) – of a primal sweet-sourness – tossed with Monterey Bay calamari, and salad (really spring) rolls ($11), stuffed with local, late-season Dungeness crab and strips of jicama.

We asked our server about the white bass ($24) – was it taken from a sustainable fishery? – and were given a vague reference to the North Coast. Halibut would have been the safer choice, especially since "California bass" can mean practically anything. But we trusted Ormsby not to traffic in endangered species, and the kitchen's handling of the filet was restrained: a simple sautéing and plating amid mussels, scallops, and pipings of aioli arranged like belts around the middle of a jolly fat man, though one doesn't really see Falstaff as an enthusiastic eater of fish.

Jack Falstaff. 598 Second St. (at Brannan), S.F. (415) 836-9239. Lunch: Mon.-Fri., 11:30 a.m.-2:30 p.m. (and weekends for Giants home games). Dinner: Sun.-Thurs., 5:30-10 p.m.; Fri.-Sat., 5:30-11 p.m. Full bar. American Express, MasterCard, Visa. Moderately noisy. Wheelchair accessible.