Scrape corn from cob and scrape cob thoroughly to get the "milk". Place corn, "milk" and water in blender. Blend a few seconds to break up kernels but do not over blend. Put this mixture through a fine sieve, pressing to extract as much liquid as possible. Put mixture in saucepan and add butter. Simmer slowly five minutes, stirring well because the corn tends to stick. Add the milk and salt to taste. Bring to a boil and add the chilies. When ready to serve, add the cheese, when cheese is melted and soup is hot serve in bowls. Garnish each bowl with deep-fried tortilla squares. NOTE: Stack six or eight tortillas on a flat surface and using a sharp knife cut them in cubes about half and inch square. Drop the cubes into hot fat and cook, stirring with a wooden spoon, until crisp and golden.