By Paul Reidinger

TOO LITTLE HAS been written about the relation between good restaurants and gay sex clubs – one of those strange-but-true symbioses, or apparent symbioses, we sometimes find in the sink pots of sensual delight we are pleased to call cities. Without getting into an excess of lurid detail about the nature of the relation, let us consider the evidence that there is a relation in the first place. Exhibit A: Market Street neighbors Mecca and Eros (a juxtaposition that sounds like the title of a Greek myth), separated only by a narrow storefront. Exhibit B: Harrison Street neighbors Mochica and rainbow-flagged Blow Buddies (no echo of Greek myth there), separated only by what seems to be a shared wall. I sat along that long wall recently (on the restaurant side, of course) and had to fight the temptation to press my ear against it and hear what I might hear.

The fight was made easier by the fact that Mochica, which opened in January, serves Peruvian food of the first rank. As recently as five years ago, you had to do some serious looking around if you wanted Peruvian food, and among the better choices was a linoleum-lined, fluorescent-lit box, Mi Lindo Perú, on a honky-tonk block of Mission Street. Then, four years ago, came golden Destino, on Market (in the old Dame space), and it was off to the upscale races. These days Mi Lindo Perú has been nicely dolled up, the small chain Fresca is on the march (from West Portal to Fillmore and, soon, to Noe Valley), the Limón people have reached out to touch mega-chic Circolo – and now there is Mochica.

Despite or because of the proximity of Blow Buddies – not to mention a freeway off-ramp that releases torrents of speeding cars onto Harrison at uncomfortably frequent intervals – the restaurant's locale seems central but suboptimal. Crossing the street is like fording an unruly white-water stream, and once safely inside Mochica, there is something vaguely surreal about watching the wine-red dining room fill with twilight while, on the other side of the large windows, men with plans – and dressed accordingly, and by that I mean you would never suppose they were on their way to the opera – stride to the next door.

Mollification, or perhaps consolation, arrives in the form of complimentary chickpeas, battered and lightly fried and mixed with a pico de gallo-like blend of splintered onions and tomatoes – a foreshadowing of potency, as it were. Chef-owner Carlos Altamirano's menu goes on to offer sequences of dishes that are boldly spiced yet elegantly simple; this is the kind of food you would be happy to eat every night, if only you knew how to make it, or knew someone who knew, like Altamirano.

Much of the food's success has to do with sauces – the coarse, guacamole-like puree of spinach and Peruvian corn that one evening accompanied a pepián de pollo ($14), say. (The chicken itself, a leg and a thigh, was braised to a confit-ish tenderness.) Camarones carlitos ($8) – big prawns still in their shells and with their heads – lay in a reddish pool of garlic, tomatoes, and Peruvian brandy that was so tasty our server brought us a pair of soup spoons to finish it off. And anticuchos of chicken ($8) – large cubes of boneless meat grilled on skewers – arrived, with quarters of Yukon Gold potato, on a plate piped with a pale green ocopa sauce that smelled and tasted strongly of mint.

The potato has been a presence in the Peruvian diet since time out of mind (the Inca cultivated the spud for thousands of years before the advent of the Europeans, who regarded it with considerable suspicion), and Altamirano honors its ancient staplehood with considerable invention. The causa rellena ($6), a potato paté layered napoleon-style with chicken, avocado, and marinated tomatoes, is particularly good – unexpected, stylish, and playfully spicy. But even the more modest crispy potatoes beside a small filet of pan-seared halibut ($7) linger in the memory.

We did find the pulpo a la oliva ($8), a ceviche-like jumble of octopus bits braised in white wine and fish broth, to be a slight dud, mainly because of the toughness of the octopus. But a real ceviche, ceviche mixto ($12), more than made up for that disappointment with a wealth of bay scallops, shrimp, and halibut (all of a buttery texture) bathed in garlicky lime juice.

For color, there is a salad of big-kernel Peruvian corn and beets ($6), the beets bringing a neon-red glow to the plate – a brightness that's belied, really, by the mildness of the other ingredients, including a curd of (just made?) queso fresco and some quartered tomato. A cilantro vinaigrette does add a welcome bit of zip.

And for dessert there are quite a few arresting possibilities. One might opt for alfajores ($6), a plate of three cookies, dusted with confectioner's sugar and filled with manjar blanco, a whole-milk spread (related, one suspects, to dulce de leche) that resembles jam. Another item not in wide restaurant circulation is a fluffy mousse ($6) of lúcuma, an orange-fleshed, subtropical fruit native to Peru. And if mousse doesn't appeal but lúcuma does, there is the banana flambé ($6) – a whole banana, peeled and caramelized and served with a dainty scoop of lúcuma ice cream, presumably made in house. If it's not the biggest dessert of all time, it's still pretty big, so you might want to share it with (sorry) a buddy.

Mochica. 937 Harrison (at Fifth St.), S.F. (415) 278-0480. Lunch: Wed.-Mon., 11:30 a.m.-3:30 p.m. Dinner: Wed.-Mon., 5:30-10 p.m. No liquor license yet but no corkage fee. American Express, MasterCard, Visa. Not noisy. Wheelchair accessible.