1Cut fish fillets into bite-size pieces. Mix fish, broth, onion, celery, carrot, tarragon, pepper and bay leaf in 1 1/2-quart saucepan. Heat to boiling; reduce heat.
2Cover and simmer 2 to 3 minutes or until fish flakes easily with fork and vegetables are tender. Stir in milk; heat through.
3Mix sour cream and flour; stir into milk mixture. Cook, stirring constantly, just until mixture starts to bubble (do not boil). Immediately remove from heat; remove bay leaf.