Black Bean and Sweet Potato Chile

2 tablespoons vegetable oil
1 medium onion, chopped
1 red pepper, chopped , (or green pepper)
4 cloves garlic, minced or pressed
2 teaspoons sea salt
1 large sweet potato, cut into 1/2-inch cubes (and peeled)
Zest and juice of 1 lime
1 28-can diced tomatoes
4 15-ounce cans black beans, rinsed and drained (or 6 cups freshly cooked)
1 jalapeno chile pepper, seeded and chopped , (or 1 can 4 oz green chiles)
1 tablespoon cumin
1 tablespoon chili powder
1 teaspoon cocoa powder

Saute the onion, red pepper, garlic, and salt in the oil over medium heat until the onion is soft, about 4 minutes. Add the sweet potato and lime zest and cook 10 to 15 minutes more, continuing to stir occasionally. Add the tomatoes, black beans, jalapeno, lime juice, cumin, chili powder, and cocoa, bring to a simmer, cover, and cook for 10 minutes or until the sweet potato is tender. Serve with lime wedges, cilantro, sour cream, cheese, cornbread, rice, tortillas, or whatever your heart desires.
The soup is delicious. I omitted the cocoa powder and the salt and made a few other changes (marked in red parenthesis).
http://www.care2.com/greenliving/
http://www.owlnet.rice.edu/~ejl4791/sweetpotatoes.html