Step 1

For marinated trout, combine ingredients except trout in a bowl. Spread half in the base of a plastic container, top with trout, then scatter remaining mixture on top, cover and refrigerate until for 1-2 hours to lightly marinate.

Step 2

For horseradish cream, whisk ingredients in a bowl and season to taste.

Step 3

Dice trout and toss in a bowl with radishes and shallot, then transfer to a plate. Whisk oil and vinegar in a small bowl, season to taste and spoon onto salad. Top with a dollop of horseradish cream, scatter with trout roe and radish sprouts, and serve with sourdough and butter.