"Borrgeo" simply translated, means "lamb" but typically, when one refers to eating borrego in Mexico, you're most likely about to partake of one of Central Mexico's true specialty dishes, Barbacoa
(Note: the following is an excerpt from Celebraciones Mexicanas: History, Traditions and Recipes, co-authored by this columnist with Adriana Almazan Lahl)
Cooking in pits is a technique that remains from pre-Hispanic times. There are records describing the Chichimeca, a fierce tribe living in central Mexico, who, when they prepared meat, hollowed out a hole in the ground which they filled with hot stones. The original ingredients were deer, armadillo, rabbit, or turkey, which were wrapped in maguey leaves. The traditional dressing is a “drunken” salsa made with pulque, and flavored pulque is offered as a drink.
As we can see from Fanny Chambers Gooch’s 1887 text, Face to Face with the Mexicans, preparation of the Mexican specialty has changed little since colonial times:
"[Barbaoca] is one of the principal articles of food known to the Mexican market—and is good enough for the table of a king. The dexterous native takes a well-dressed mutton, properly quartered, using head and bones. A hole is made in the ground and a fire built in it. Stone slabs are thrown in, and the hole is covered. When thoroughly hot, a lining is made of maguey leaves, the meat put in, and covered with maguey. The top of the hole is also covered, and the process of cooking goes on all night. The next morning it is put in a hot vessel, ready to eat—a delicious, brown, crisp, barbecued mutton. As the process is difficult and tedious, it is generally prepared in the families, and even the wealthiest patronize the market for the delicacy, ready cooked".
Lucky San Franciscans can find real borrego in rustic street tacos at La Vallarta 3039 24th Street 415-826-8116 for $2 a pop. For a more upscale experience, you won't want to miss the delicious Goat Barbacoa Tacos at Padrecito (same owners as Mamacitas, see my review here), goat barbacoa, served with avocado, kale sprouts, salsa arbol, crema Mexicana y Queso Manchego, two for $13. (They also serve great cocktails, see Drinks in the City for more info).
For adventurous chef's, there is a recipe in Celebraciones Mexicanas which describes
placing goat or lamb plus all the fixin's wire rack in a pan on top the vegetables and beer, leaving space below for the meat juices to drain into the pan (which creates an amazing Caldo de Borrego or Goat or Lamb Broth); placing banana leaves on the wire rack and then placing the meat on top of the banana leaves and covering the meat well with more of the banana leaves, then placing a second foil cooking pan upside down over the first as a lid, sealing it with a mixture of masa harina or a mixture of flour (covering masa harina or flour mixture with foil paper taking care to wrap the edges of the pans to protect the "package" from burning and falling apart. This procedure will prevent steam fromescaping from the cooking pans and will create sort of a pressure cooker, effectively locking the juices inside the pans). Your Barbacoa will then cook in the oven at 375°.