Finely dice trout fillet. Mix lime juice with horseradish, add pieces of fish.
Clean and wash the celery and spring onions and cut both into very fine cubes. Core the chilli pepper and chop very finely. Mix the butter with the rose paprika.
Mix the marinated trout pieces with the celery, chilli pepper and spring onion. Brush the Pumpernickaler with paprika butter. Spread the trout tartare on top with a small spoon. Sprinkle with the chives.