Heirloom Cafe in the Mission can come on strong -- but knows when to hold back deliciously, as in this dish with PEI mussels

PHOTO BY RORY MCNAMARA

paulr@sfbg.com

DINE The Gospel According to Matthew offers no restaurant commentary I'm aware of, but it does remind us that "you will know them by their fruits" — the King James Version of the holy book gives us the fruitier "ye shall know them by their fruits" — especially (to make a slight inference) heirloom fruits. Or restaurants. If you want to know what a neighborhood is like and how it might be changing, you look at the restaurants.

Recently The Wall Street Journal ran a story suggesting that the Mission District is rapidly being colonized by techsters who live in the city and commute to jobs on the Peninsula in shuttle buses provided by their employers, among them the colossi Google and Apple. The map showed the corporate bus stops, though not the location of Heirloom Café, which opened in April in a gorgeous box of a space at Folsom and 21st streets. But if the shuttle-bus routes are adjusted so that the techsters can be dropped off there and go straight in to dinner, I won't be surprised.

Heirloom is the kind of place that, five or six years ago, you would have expected to find opening in Glen Park or outer Noe Valley. It is a respectful, conscientious restoration of an old Victorian space, with wood-plank floors, cream-colored walls, lots of natural light, ceiling fans, and tables (including the long communal table) simply but handsomely dressed with white linens. Its menu is refreshingly brief and implies a lineage, at least in spirit, from Chez Panisse and Zuni Café.

But it is an odd experience, I must say, to stand on the sidewalk outside the door and watch the local world go by. Heirloom sits in the very heart of the Mexican Mission, and might as well be the embassy of some faraway country no one has heard of. The neighbors pass by with scarcely a glance at the place or the menu card posted in the window. The people who do pause, and then step inside, all seem to be wearing Dolce & Gabbana eyewear, or at least look as if they've tried on a pair or two. Worlds collide, sometimes, but they can also coexist, in the same time and place, as if in parallel universes.

The cooking is as elegant and understated as the interior design. Small touches make a big difference, as in the wonderfully crisp matchstick frites scattered over a salad of smoked trout ($12), frisée, and haricots verts. The fries brought a lovely lightness and crunch to an already complex salad. A mushroom tart ($10) was similarly, subtly enhanced by the tang of bacon. The pastry crust had the tender snap and tastiness of real butter.

On occasion, the magic ingredient goes missing, as with the mussels ($10). These were served with a classic white wine broth, which was a little sharp and sour, especially if you've been spoiled (as I have) by such innovations in this area as Thai-style red curry or beer-with-chorizo broths.

And some special ingredients won't be to every taste. The burger ($12), for instance was served on an English muffin in the presence of pickled carrots, but the dominant reality was the epoisses cheese, whose ripe pungency gave pause. At first bite I wondered if the meat had spoiled — the cheese was that strong. I continue to question the French-style cheeseburger, I must say. High-quality beef generally doesn't need much support, let alone interference.

A nice illustration of knowing when to leave well enough alone involved the poached halibut ($22), which turned out to be nearly as rich and creamy as the potato purée it was served on. Halibut is something like the perfect fish — meaty and substantial, mild-flavored but not bland, wild but taken from well-managed fisheries. To find it handled with restrained grace is the jewel in the crown.