Peel cucumber so it has alternating green stripes and thinly slice into rounds, place it in a bowl and sprinkle a little salt. Toss the cucumber with your fingers and let sit for 15 minutes.
Pour any liquid that’s sitting at the bottom of the bowl and gently squeeze the excess water from the cucumber slices.
Soak the wakame in cold water for a few minutes, drain well and add it to the cucumber slices.
Whisk in all the ingredients for the dressing into a bowl add it to the salad, together with the sesame seeds (optional).
Toss well, transfer to small serving bowls and top with shirasu / whitebait (optional). Enjoy!