Heat a fring pan and add the rapeseed oil, do not allow to burn. Place fish into the oil and gently press down to settle into the heat. Do not stir/move. Leave for 3 minutes. Add the butter, cut into small cubes, into the pan, not on the fish, and allow the foam and turn a little golden ('Beurre noisette') Then spoon the butter over the fish to finish cooking. Remove the pan from the heat when the fish has lost transarent appearance add all the other ingredients into the butter, Stir and serve.