Prep: 15 minutes, plus overnight soaking; Cook: 6 1/2 hours.
Wash beans thoroughly, soak overnight, and drain.
Place beans in slow cooker. Add water and next 7 ingredients.
Cook on LOW for 6 hours, till beans are tender.
Brown the meat well in a frying pan for 8 minutes. Stir in tomato paste and cook 1 minute. Then add the steak, peppers, corn, tomatoes, and salt to the beans, and cook an additional 30 minutes. If desired, add more chipotle chili powder for more heat.
Garnish with low-fat sour cream, if desired, and the fresh chopped cilantro.