MELT butter in saucepan on medium heat. Whisk in flour; cook about 4 min. or until blond colored. Do not brown the roux. Cool.
BRING 2 qt. of the reserved corned beef cooking liquid to a boil in large pot (or 1 qt. cooking liquid for trial recipe). Cook until liquid is reduced by 1/4. Stir in milk; bring to a light boil. Add roux; simmer 30 min., stirring occasionally.
STIR in corned beef; simmer 20 min. Reduce heat to very low. Stir in cheese, sauerkraut, dressing and caraway; simmer 10 min.
PORTION 6 oz. into each bowl and garnish with 2 Tbsp. each croutons and cheese.