For the filling, roughly pluck the trout. Squeeze lemon. Puree trout, half juice, cream cheese and horseradish in a high mixing bowl with a hand blender. Season to taste with salt and pepper.
Lay out the work surface with two layers of cling film slightly overlapping. Place salmon slices on top. Wash basil, shake dry, pluck leaves from the stalks and spread on the salmon.
Spread trout cream evenly on top and roll up the salmon plate. Keep cold.
In the meantime wash the salad, drain well and pluck a little smaller if necessary. For the rest of the vinaigrette, mix lemon juice, salt, pepper and 1 pinch of sugar. Fold in the oil. Mix vinaigrette and salad leaves.
Spread on a plate.
Cut the salmon roll with a sharp knife into about 12 slices. Arrange the slices on the salad and sprinkle with some pepper. Baguette goes well with it.