In a large soup pot over medium heat, warm the oil. Add the next four ingredients; cook, stirring occasionally, about 5 minutes. Add 1/2 cup water, reduce heat to low, and continue cooking 12 minutes, or until the onion is softened. Pour in the beans plus their liquid, coconut milk and, 2 1/2 cups water. Increase heat to high and bring to a boil. Reduce heat to medium-low and simmer for 15 minutes. Puree a cup of the beans until smooth, then return them to the soup, stirring to thicken.
Garnish with cilantro and lime