Directions

1. 1. Cook beans according to the basic instructions .
2. 2. While beans are cooking, prepare the ancho chili puree: If you're using whole chilies, toast them in a 200° oven for 5 minutes, remove seeds and stems, and soak in 1 cup hot water for 15 minutes. In a food processor, process the chilies to a thin puree with half the soaking watet. If you're using the ancho chili powder, mix it with 1/2 cup of water.
3. 3. In a medium saucepan over moderate heat, heat the vegetable oil. Cook the onion and garlic for 5 minutes. Add the chili puree or the chili powder—water mixture, chipotle, and ground cumin. Add the tomatoes, stir up the bottom of the pan, reduce heat to low, cover, and simmer for about 40 minutes.
4. 4. When the beans are done, drain them in a colander and add them to the sauce. Stir well. (If the dish seems dry, add a little water and simmer for another 2 minutes.) Remove the chipotle, and add the salt. Top each serving with cilantro and sour cream.