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, Ruben, 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 Folklorico, 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 te de cafe (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 Iztaccihuatl. 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 vizcaina, 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.

We follow Josefina past a man in a black cowboy hat and elegant silver-rimmed glasses who has his boots up on a table, hiding behind a stack of chicharrones (fried pig skins) as he reads an adult comic book. She stops at a stand to buy mole pastes, arranged in little mountains of brownish red, caramel, and green. These pulverized mixtures of many ingredients—among them nuts, herbs, spices, chiles, chocolate, tortillas, and white bread—are diluted with stock, creating rich sauces. Because good-quality pastes are easily found in markets, and because, with up to 25 ingredients, they are very labor intensive, even women like Josefina—for whom "from scratch" is a way of life—choose to start with a paste and doctor it to make it their own.

On our way out, we sit down for quesadillas of mushrooms, cheeses, and tinga, made by a stout woman, her hair pulled back into a low bun. But Josefina is still shopping. A shy girl approaches us with nopales, which are reputed to have many health benefits, among them the lowering of cholesterol. Josefina gets several bags of the cactus, not only for the romeritos but also because Pepe, having acquired the dietary consciousness of an American, will certainly request a few simple nopales salads.

For the next two days, Josefina's ayudantes (helpers)—who include her posse of daughters and Marta, the widow of her late husband's son by his first wife (who, thanks to Josefina's generous definition of family, is an integral member of the group)—will run to the market after Josefina finds she needs more milk or a can of chiles or whatever. They will wash and peel and shell and boil. They will cut onions into a perfect quarter-inch dice, the way Josefina taught them. They will take down large pots from high shelves; they will lift heavy roasts from the oven. They will do what they are asked with tremendous love and respect and a good deal of competence. But none of them has what Pepe calls el toque, the touch.

On the day before Nochebuena, Marta begins the cooking by toasting dried shrimp for the romeritos, the most time-consuming dish. Josefina drains the salt cod, which has been soaking in water all night long, and then, with her small, sure hands, long nails painted pink, begins removing tiny bones. Claudia, the youngest daughter, pulls up her sleeves and takes over so that Josefina can make the marinade for the ham. Pulling out a drawer filled with bags of dried chiles, she finds one of ancho and dumps the contents into a hot skillet to toast; and a fragrant, smoky smell wafts through the small kitchen, filled with her own busy elves.

The next morning, Josefina is, as usual, the first one up. Claudia, then Sylvia, then all the others come down, one at a time, to find her in the kitchen, where she is just finishing the picadillo—a mixture of ground pork, nuts, candied citron, and spices—that she will use to stuff the turkey. Josefina gladly stops what she is doing to give the benediction to each of her grown children as they leave to do last-minute gift shopping. They stand before her, eyes closed, hands at their sides, as they must have done ever since they were small.

Josefina and Marta put the turkey into the oven, then the ham, smeared with chile marinade. Midday, the phone rings: it's Pepe, calling to say that the airport is open and his flight will be on time.

Toward evening, the daughters trickle in, laden with bags, and the whole family goes upstairs to get ready. Lilia is drying her hair and Claudia is sitting on the bed with a compact mirror, applying heavy coats of mascara and makeup, when the bell rings. The little grandsons squeal and race to open the door. Pepe's sisters, every one of them in high heels and dresses, run downstairs after the boys and then stop, standing back from the door as if they'd encountered a magnetic field. Pepe, dressed like an American businessman, with a pocket-square and cuff links, a Cohiba cigar firmly gripped in his manicured fingers, walks through the doorway as though he had walked through it yesterday evening and every evening before that. He peels his nephews off and greets each of his sisters with a kiss as he passes through them, as if parting the seas, on the way to his mother, who waits patiently by the kitchen.

He hugs her big, and she looks at him as if to inspect and admire this grown man of hers. Within minutes she's poured him a shot glass of tequila. Then it's time for her to walk the two blocks to evening mass, flanked by Rosalba and Sylvia, who, like the rest of the family, are not particularly devout but respect their mother's piety.

It is near midnight when they return. Pepe sits with his cigar, playing all kinds of poking and tickling games with his nephews while the women go into motion to get the food onto the table. At last they gather around, Pepe standing next to his mother, his arm around her shoulders, his face a near-replica of hers. She gazes happily up at her firstborn, then out at the feast and family that lie before them. Pepe reaches into the bacalao, sneaking an olive, and then smiles back at his mother like a little boy who knows he couldn't possibly get into trouble tonight. It's Christmas.