You can already prepare the beetroot mousse a day before. Chop the beetroots, then blend until smooth. Keep a few bigger beetroot slices for later.
Mix beetroot with horseradish, cream cheese, sugar, salt and pepper.
Soak the gelatine leaves in a bowl of cold water for 5 minutes until soft. Remove from bowl and excess water. Slowly warm the gelatine to a low heat, then stir through until the gelatine has completely dissolved.
Stir the gelatine into the cream cheese mix.
Whip the cream and fold into the mixture. Chill the mousse for at least 3 hours in the fridge.
Heat a pan with some oil. Toss some nuts into the pan and spread them out flat. Add some mustard, honey, lemon juice, 1 tbsp water, salt and pepper. Let them sit for about 5 minutes and then toss them around. Keep stirring until they have little toasty marks on them.
Before serving the mousse, stir the mixture again with a whisk. Add a slice of beetroot in a steel food ring. Then place some mousse on top of that. Remove the ring, then arrange trout and salad on plate and drizzle with the dressing. Garnish with a little dill for a finishing touch.