In a large saucepan, cook bacon until crisp; drain. Add potatoes, broth, carrrot, onion, parsley, celery seed, salt and pepper. Cover and simmer until potatoes are tender, about 15 minutes.
Combine flour and milk until smooth; add to soup. Bring to a boil; boil and stir for 2 minutes. Add cheese; stir until cheese is melted and soup is heated through. Garnish with green onions, if desired.