This recipe is adapted from one in Vincent and Mary Price's "A Treasury of Great Recipes." Although it appears amongst those from the Rivoli Restaurant in Mexico City, it doesn't appear to be from the restaurant itself. "This hearty soup, a sort of Mexican minestrone, is made with both [corn and chiles], as you might expect, but it is the unexpected ingredients that make it so good." Let me tell you... this soup is OUTSTANDING. I've made a lot of soups, and this is one of my favorites. I'll be making it often in years to come!