Peel the radish and cut into wafer-thin slices with the mandolin. Arrange the salmon with the radish slices on the plate.
Mix the mustard with the water and the chilli powder to make a sauce. If you like and need dill with salmon, you can cut up fresh dill and add it or add dried dill (with the latter I would let the sauce rest a little). Pour this sauce over the radish and salmon carpaccio.
Finally, pour black pepper from the pepper mill over the carpaccio and garnish with the olives.