If using fresh corn, use a sharp knife to cut off just the kernel tips, then scrape the cobs with the dull edge of the knife. (You should have 3 cups corn.)
Place 1-3/4 cups corn in a food processor bowl. Cover and process until smooth; set aside.
In a large saucepan cook onion and celery in hot oil until onion is tender but not brown. Stir in chicken broth and potato. Bring to boiling; reduce heat and simmer, covered, for 10 minutes. Stir in the corn puree and the remaining corn. Cook, uncovered, about 10 minutes more or until potato and corn are tender, stirring occasionally.
In a small bowl combine milk, flour, pepper, and ground red pepper; stir into corn mixture. Cook and stir until thickened and bubbly. Cook and stir 1 minute more. Stir in ham and cheese; cook and stir until cheese melts and soup is heated through. Garnish with parsley. Makes 5 servings.