In a 4 quart pot, saute the onion with jalapeno in a tablespoon of oil.
Add in the beans, salsa, chicken broth, and bring to a boil
Mix cornstarch with water and slowly stir into slowly boiling soup. (the soup will thicken)
Add in lime juice and cilantro.
Puree with an immersion blender until smooth, or add 1 can of black beans and puree, then add the second can of black beans if you prefer it chunkier.
Serve topped with cheese, sour cream, and cilantro.