In a large skillet, layer the cucumbers, onions, celery, parsley and dill; pour broth over all. Top with fillets; bring to a boil. Cover and simmer for 8-10 minutes or until fish flakes easily with a fork.
Transfer fish to a serving platter and keep warm; reserve cucumber mixture in skillet. Combine cornstarch and cream until smooth; add horseradish. Stir into skillet. Simmer for 2 minutes or until thickened. Pour over fish; serve immediately.