I’m eating a glorious dish of pork ribs in chile negro. It’s Mexican, but I have never tasted anything like it before, not even in Mexico.

The Sauce for these remarkable costillas (ribs) is dark and sweet, like mole, but not as redolent of fruit, nuts and sesame. It owes its color to dark chocolate and the long, slim, black pasilla negro chile.

Even more remarkable, I am eating this dish right here, in Los Angeles, where Mexican food is so often ordinary and disappointing.

The place is Teresitas Family Restaurant in East Los Angeles, a longtime hangout for politicos and police, as well as for people from the neighborhood who know how good the food is.You don’t go to Teresitas for obscure, regional Mexican dishes, but for familiar food prepared exceptionally well. It’s homey and comfortable, like a big coffee shop. There’s a painting of Don Quixote on one wall, a Mexican village scene on another. But decorations aren’t important. It’s the food that counts.

Teresitas does a smart thing. Rather than trying to serve everything every day, it allots one day a week to its very best dishes, such as the costillas – the full name is costillas de puerco en chile negro. That way, the kitchen can concentrate on doing a superlative job, and there’s always something different to eat. Customers divide into groupies who come when their favorite dish is on hand: Wednesday for the costillas, Tuesday for albondigas and Thursday for mole poblano.

Teresitas was little more than a taco shack when the Hernandez family opened it in 1983. Teresa Hernandez Campos did the cooking, and her kids came after school to help. Hernandez, who was born in Zacatecas, is still in the kitchen, and son Antonio runs the dining room. He’s a friendly guy who walks from table to table to see how you like the food and sometimes brings samples of a dish.

Everything I have eaten here has been top-notch, even the beans and rice. In Mexican restaurants, if these are good, it’s a sign that the rest of the food is likely to be superior. The beans are frijoles rancheros, boiled beans seasoned with tomato, onion, chile, vinegar and oregano.

The rice is fried until toasted, then cooked with chicken broth.Rice comes on the side with albondigas or caldo de pollo (chicken soup). In Southern California Mexican restaurants of the more authentic stripe, the custom is to stir a spoonful into the soup, then brighten it up with splashes of Lime juice and salsa.