For a healthier version of this crema, try using nonfat Greek yogurt instead of the sour cream. Slideshow: More Quick & Easy Soups
In a large Dutch oven or stock pot, heat the oil. Sauté the onion over medium-high heat until soft, 5 minutes. Add the garlic, cumin and 1 teaspoon salt. Cook until fragrant, 2 minutes.
Stir in the black beans, stock and chipotle, scraping up any brown bits from the bottom of the pot. Bring to a boil and simmer over medium-low heat until the beans are tender and the soup has thickened, 20 minutes.
Remove from the heat and add the lime juice. Transfer 2 cups of the soup to a food processor or blender and puree until smooth. Return to the pot and taste for seasoning.
In a small bowl, combine the sour cream and cilantro. Season with salt and pepper.
Ladle the soup into bowls and serve alongside the cilantro crema.