Bring first 6 ingredients to a boil in a Dutch oven. Cover, reduce heat, and simmer 20 minutes or until potato is tender. Stir in corn; remove from heat.
Melt butter in a heavy saucepan over low heat; add flour, stirring until mixture is smooth. Cook, stirring constantly, 1 minute.
Stir in milk and next 5 ingredients. Cook, stirring constantly, until cheese melts. Gradually stir cheese mixture into vegetable mixture.
Cook over medium heat, stirring constantly, until soup is thoroughly heated. Garnish, if desired, and serve immediately.