In a blender, combine half of the corn and the broth. Cover; blend until nearly smooth.
In a large saucepan, combine corn puree, remaining corn, chiles, butter (or margarine), garlic, dried oregano (if using), salt and pepper. Bring to boiling; reduce heat. Simmer, uncovered, for 10 minutes. Stir in milk, chicken, tomatoes and snipped oregano (if using); heat through. Remove from heat. Stir in cheese until melted. If desired, sprinkle individual servings with snipped parsley and garnish with oregano sprigs.