Put the fennel in a shallow serving
dish and scatter over the apple, spring
onions and beetroots. Flake the trout
into chunky pieces and arrange on top.
Sprinkle with half the dill fronds. Finely
chop the remaining fronds and reserve.
Mix the yogurt and horseradish with
1 tbsp cold water, then stir in the
reserved dill. Pour half the dressing over
the salad and toss very lightly. Spoon
over the remaining dressing and serve.