Although no two cooks prepare a pupusa in exactly the same fashion, the standard version consists of a flat bread that resembles a fluffy tortilla stuffed with white cheese, grilled on a griddle until crispy golden outside and gooey inside, and then topped with curtido, a spicy relish of pickled cabbage.

Just one oozing bite is usually all it takes to start a serious addiction. Luckily it's a cheap habit: As pupusas run about $1 to $2 a pop, there's no reason not to sample every variety of pupusa filling, including frijoles (beans), camarones (shrimp), chicharrón (pork), and loroco, a tasty green vegetable blossom that is native to El Salvador and other parts of Central America.

Finding a good pupusería may be as simple as checking your local phone book, but those with a fervent hankering to savor the Salvadoran snack should head to San Francisco's Mission District, where enough of these establishments dot the landscape to enable a serious pupusería crawl. El Zócalo (3230 Mission Street, 415-282-2572) is a favorite with local families and late-night revelers, offering hearty pupusas in both corn and rice flour versions, plenty of cheap beer, and a friendly, low-key atmosphere every night until 3 a.m.

Diners looking for a more upscale experience can try Panchita's 3 (3115 22nd Street, 415-821-6660), the third in a triumvirate of like-named Salvadoran restaurants. Here, candles flicker across white tablecloths laden with camarones en mole verde (shrimp in green mole, a lively sauce) and delicate almond flan in a strawberry coulis. But in keeping with the Salvadoran spirit, the pupusas are still a populist-pleasing $1.75. ¡Que bueno!