Wash, peel and quarter the apple and remove the core. Grate the apple and immediately mix in the lemon juice. Peel the horseradish and grate finely. Cut the cress.
Mix the cream with the honey. Stir in apple, horseradish and cress. Season the sauce with salt.
Divide the fish fillets in glasses. Pour the sauce on the fish and decorate with a little cress.