Boil the potatoes until cooked, drain and allow to cool a little. Fry off the trout fillet on both sides. In a bowl, mix the yoghurt, lemon and chives. Season and grate the horseradish to you liking and mix.
Cut the potatoes into bite sized pieces and just before serving.
Toast the pinenuts, then cut the beetroot and shallot to the same size as the pinenuts. In a bowl, mix together all the ingredients, add the tarragon and make a sweet dressing with oil, maple syrup and balsamic vinegar and season to taste.
Mix the potatoes and yoghurt and make a small bed on a plate. Place the fillet on top and dress the beetroot dressing around.