Remove the salmon from the marinade and drain on absorbent paper.
Slice the salmon chunks into a few thick slices each. Place the salmon and potato slices on serving plates. Sprinkle a little sel de Guérande and black pepper on each. Arrange a couple of pieces of carrot and onion on top of the salmon and potatoes, followed by a few drops of oil from the marinade. Finally, sprinkle some chervil over each serving.