Costillas de ResSlow-cooked beef short ribs are typical of the rustic cooking style of northern Mexico's cattle country. Look for lean, meaty well-trimmed ribs in specialty meat markets, and ask the butcher to cut the ribs into 3-inch pieces. Short ribs are pretty tough, but have great flavor if cooked long enough to get really tender. Serve with soupy beans (Basic Pot Beans) and Fresh Salsa Mexicana.