1. Put the wakame seaweed in a small bowl and cover it with cold water. Stand for 5-7 minutes until the wakame softens. Drain and squeeze the water out.
2. Boil the prawns with a little water and a pinch of salt for two minutes or until just cooked. Let them cool down then de-shell and halve length-ways (if the prawns are small there is no need to cut into two).
3. Mix the rice vinegar, soy sauce, mirin and sugar together in a bowl making sure the sugar dissolves and then add grated ginger (optional). Roughly peel the cucumber and halve lengthways, cutting off or scraping out the seeds. Slice them thinly and diagonally. Add these to the dressing. Thinly slice the ginger, then collect the slices together and slice again to make needle thin. Place this in the bowl with the dressing and cucumber. Slice the shrimp into about three pieces and then add to the bowl. Add the wakame seaweed and mix all the ingredients together, throwing in a sprinkle of sesame seeds.
You are now ready to plate up.