Wash the potatoes and cook in plenty of boiling water for about 20 minutes. Pierce the eggs, put them in plenty of boiling water and cook for 10 minutes. Quench eggs under cold water and let them cool down. Drain potatoes, rinse with cold water and peel. Cut potatoes into slices.
Peel onion and chop finely. Heat stock, vinegar, diced onion, some salt and pepper in a pot. Mix crème fraîche, yoghurt, horseradish and some salt. First mix the hot vinaigrette into the lukewarm potato slices and let it stand for about 5 minutes. Then add the horseradish sauce and capers, fold in and let the salad stand for at least 1 hour. Peel the eggs and cut into pieces. Cut salmon into strips. Wash chives, dab dry and cut into fine rolls. Mix salmon, eggs and chives into the salad, except for a little bit for sprinkling.
Peel the eggs and cut into pieces. Cut salmon into strips. Wash chives, dab dry and cut into fine rolls. Mix salmon, eggs and chives into the salad, except for a little bit for sprinkling. Season with salt and pepper and arrange on small plates. Sprinkle with remaining chives