PREPARATION:

1. Combine water, potatoes, celery and carrot in medium saucepan. Bring to a boil over high heat. Reduce heat to medium; simmer, uncovered, 10 minutes or until vegetables are tender.
2. Meanwhile, melt butter in large saucepan over medium heat. Cook and stir onions in butter 2 minutes or until tender but not brown. Stir in flour, salt and pepper. Cook and stir about 1 minute.
3. Stir milk and potato mixture into flour mixture; cook and stir over medium heat until bubbly. Cook and stir 1 minute more. Stir in cheeses and caraway seeds. Reduce heat to low; simmer, uncovered, until cheeses are melted and mixture is hot, stirring constantly. Garnish with chervil. Serve with oyster crackers, if desired.