Like a Greek Hydra, Michael Psilakis’s miniempire lost one restaurant this year and grew back two. The beloved original flagship, Onera, closed recently, but up has sprung Kefi to take its place at the same address, while Anthos has opened in Midtown.

Anthos sticks to the high-end, innovative Greek fare pioneered at Onera, while Kefi offers plainer food at bargain prices. The latter appears to be just what the Upper West Side has been waiting for. No menu item tops $16, glasses of wine are $6, no reservations and no credit cards are accepted, and the cozy basement restaurant is an open secret: On any given night, Kefi (whose name translates to “exuberance”) packs in more customers by far than Onera (whose name means “dreams”) ever did in the same space, and has to turn away even more. That’s good news for the owner, but not always so wonderful for the patrons who have to wait up to an hour, standing in the crowded entryway, for a table.

Though Mr. Psilakis made his name with inventive, modern Greek-inspired preparations involving raw seafood, delicate organ meats, and carefully assembled flavors, little of that is evident at Kefi. These are casual, classically minded dishes, without the modern kiss that made meals at Onera so special. By far the best offerings are among the dozen small plates, treats of which a meal can and should be made. Tender, coarse-ground meatballs ($5.95), compounded of pork for lightness and lamb for flavor, swim in a hearty tomato sauce whose herby, oniony richness no normal eater could bear to leave unsopped after the meatballs are eaten. The dish is substantial, too. One order, eaten with bread, would make a meal, or close to it, if you can resist your tablemates’ entreaties to share.

A plate of wonderful fried sweetbreads ($7.95), together with artichoke hearts and crisp shallots, is a tasty reminder of the five-course offal tasting menu that used to emanate from the same kitchen. If the nostalgic pangs are a bit overwhelming, a second helping of the sweetbreads can be a great comfort. Classic fare — spanakopita, taramosalata — receives a fine treatment: The spinach pie ($4.50) is open-topped to display fresh, whole spinach leaves doused in nutmeg-warmed cream, and a shareable spread of spreads includes zesty takes on tzatziki and smoky eggplant purée, as well.

Mussels ($6.95) share a thin, creamy sauce with succulent broad beans that resemble another sort of sea animal: The two are fast friends, brininess and earthiness melding in the lemony, garlicky broth. Land and sea come together again in an unusual plate of whole cuttlefish ($8.95) stuffed with tangy, melty manouri cheese that squirts out under the pressure of a knife, and seated on rounds of sunny-tasting roast tomato. The cuttlefish are softer, richer cousins of squids, plump with cheese and pale in color, with appealing little chewy knots of tentacles sticking out behind them. Batter-fried calamari and grilled octopus round out the menu’s selection of delicious Mediterranean cephalopods.

The smart move is to end the meal there. Many of the simple main courses have an unmistakable lack of panache signaling that the chef’s attention is elsewhere in his empire. Tossed casually on the plate, they get no points for presentation, and unfortunately they don’t make up in flavor what they lack in style. On my visits, the big braised lamb shank ($15.95) was tired and nearly tasteless, outshined by the zingy tomato-soaked orzo it was served with; a dryish pork souvlaki sandwich ($13.95) was little better, and its side of creamy rice had an undercooked crunch. If a Greek kitchen is so overtaxed that it can’t boil rice, perhaps its frantic no-reservations policy should be rethought.

A few main courses are better: toothsome twists of pork, stewed with lemon, peperoncini, and caperberries ($12.95), for instance, even if they’re a little tougher than ideal. A macaronia section of the menu includes a casual eggplant-potato moussaka ($11.95) with good cinnamon flavor but very little structure — certainly not the elegant layers one often finds — and a decent, similarly seasoned dish of square noodles with braised rabbit. Crisped shallots tossed on top are a small touch that adds a great deal.

A sort of custardy cheesecake ($5.95) is the best of the desserts, rich and complex, with a hint of salt — I can only imagine how good it would be if the kitchen had the leisure to make one that wasn’t misshapen and burnt. The walnut ice cream tasted burnt one night too, but not on a return visit; the crumbly walnut cake it accompanies ($5.95) is consistently delicious.

The bargain-priced all-Greek wine list does its job. While a wider-ranging selection might offer more enjoyment, the $6–$10 glasses allow plenty of experimentation. As with the rest of the meal, the wine is good enough for the price.

Kefi (222 W. 79th St., between Broadway and Amsterdam Avenue, 212-873-0200).