This recipe freezes well, too, for great leftovers.
1. Warm the oil in a large pan over medium heat and add the onion, garlic, and salt. Saute until soft, about 4 minutes.
2. Add the sweet potato and lime zest, and cook 10 to 15 minutes more, continuing to stir occasionally.
3. Add the tomatoes, black beans, jalapeno, lime juice, cumin, chili powder, and cocoa, bring to a simmer, cover, and cook for 10 minutes.
4. Serve over brown rice, if desired, with lime wedges and cilantro, or with corn bread, biscuits, or taco chips alongside.