Combine onion, celery, bell pepper and butter in 4-quart saucepan and cook until
vegetables are softened, about 10 minutes. Add flour and cook 5 minutes,
stirring occasionally. Add bay leaf and stocks. Bring to boil, reduce heat and
simmer.
Cut corned beef into julienne strips and add to soup. Add cheese and stir slowly
until completely melted. Add sauerkraut. Gradually add roux and let soup simmer
30 minutes. Add scalded half-and-half. Remove bay leaf.
Ladle soup into bowls and top with croutons. Top each serving with a slice of
cheese.