Doña Josefina Figueras Viuda de Carreño (my step-grandmother) steps into the living room in a pink flowered apron, dirty from the day's work. "Siempre en la cocina," she says, smiling a tired, contented smile—always in the kitchen. It is 10 p.m. on the night before Nochebuena (Christmas Eve) in Mexico City, and Josefina has come out of her kitchen, where she's been since seven this morning, because her four grown children have called for her to watch the TV update on "el Popo", Popocatépetl, the volcano 45 miles southeast of here that has been threatening to erupt. The news today is that, because of increased volcanic activity, the airport in Mexico City may close. This is of particular concern in this family tonight because mañana Pepe viene—tomorrow Pepe comes.

Pepe is Josefina's first child and the only one of her five whom she does not see every day of the world. (Three—along with two grandchildren—live with her in this tight but comfortable three-bedroom house, and the fourth visits every night for cena, the late-evening snack. Her sixth child, Rubén, lived with her as well but recently died.) Pepe lives in Washington, D.C., where, for the past 11 years, he has reported on American politics for the Mexican newspaper El Universal. He visits his family (my distant family) twice, maybe three times, a year. I've been here a week, on my first long visit, and the words cuando Pepe venga (when Pepe comes) have been repeated like a mantra ever since I arrived.

Cuando Pepe venga, his sisters tell me, we'll have a fancy lunch downtown at Casa Bell. Cuando Pepe venga, we'll go to the Ballet Folklórico, at the Palacio de Bellas Artes, where Sylvia, the oldest sister, is general manager. Cuando Pepe venga, their mother will plug in the espresso maker that Pepe gave her a few years back because the only thing she makes that he dislikes is her percolated, decaffeinated coffee, which he calls té de café (tea of coffee). And cuando Pepe venga, Josefina will prepare all the family favorites: shrimp soup; roasted poblano chiles stuffed with cheese and baked in rice; and, of course, Christmas standards like fresh ham with red chile marinade and roast turkey stuffed with the spiced ground pork mixture called picadillo.

Even in a country where good home cooking is commonplace, Pepe has told me, Josefina's food is exceptional. He talks of little else when he talks about going home. When he invites me to come, too, he entices me by describing the succulence of one of her specialties, tinga—shredded pork with chiles. "My mother makes the best tinga," he says, closing his eyes. "Mmmm. There's nothing like it."

Mexico City rests in a dry lake bed on the top of a plateau, at 7,350 feet above sea level. Its notorious air pollution makes breathing difficult, even painful, and turns this vast cityscape into nothing but shades of gray. There are gray parks and squares, regal gray architecture, and gray stone churches on every block. "Mexico City is an ugly city with a lot of beautiful places," Pepe once told me. In fact, the city is not ugly; it just looks ugly most of the time. It isn't until we are blessed with a clear day that I realize how different the buildings look against a bright blue sky, and how the Christmas lights, strung across streets downtown, sparkle—even from a distance.

In preparation for Pepe's arrival, Josefina, three of her four daughters, and I walk, on this crisp December day, to the tianguis, or outdoor market, in their neighborhood of Iztaccíhuatl. At the market Josefina is instantly transformed from a hesitant septuagenarian who takes her daughters' arms when she crosses the street into a strong, quick shopper who knows exactly where to find the best ingredients for the Nochebuena feast.

We reluctantly pass a vat filled with elote (corn)—sold slathered with mayonnaise and sprinkled with chile powder and soft, tangy queso fresco (fresh cheese)—in order to keep up with Josefina. She strides past numerous produce stands piled with romeritos, stringy green vegetables that taste like spinach, before finding a satisfactory vendor. The bagfuls she buys will go into an elaborate dish that also contains potatoes, nopales (cactus paddles), mole sauce, and fried shrimp cakes. Romeritos is a centerpiece of Christmas tables throughout the city, but it is not the first thing the members of this family will reach for. The first dish they will want and the one they will ask for seconds of is the bacalao a la vizcaína, salt cod cooked with onions and tomatoes and mixed with almonds, pickled chiles, and green olives—lots of them, because everyone in the house has a habit of picking them out before the dish makes it to the table.

Josefina crosses the central aisle, where the tails of piñatas—green and red and silver and gold—hang low, to visit the cheese man, wearing a red (yes, red) Yankees cap. He smiles and dips deep-fried tortillas into vats of crema, the sweet, buttery Mexican cream, sprinkles them with queso fresco, and hands one to each of us. While we snack, he takes care of Doña Josefina, who rattles off an order starting with many cups of crema and adding nearly every one of the cheeses he offers, including a few plastic-wrapped slices of queso americano.