Melt the butter in a large stockpot over moderate heat. Saute the onions until soft, about 10 minutes. Add the garlic, coriander, cumin and jalapeno pepper and saute another 2 minutes to release the aromas. Add the chopped tomatoes and cook until they are juicy. Add the potatoes, bell pepper, salt and pepper, and stock. Cover and simmer until the potatoes are tender, about 10 minutes. Add the corn and heat through another 2 minutes.
In a blender, puree half of the soup with the milk and cheese. Stir the puree back into the soup pot. Adjust seasoning. Heat slowly until soup is warmed through and serve.
c.1997, M.S. Milliken & S. Feniger, all rights reserved