Wash the cucumber, cut it in half lengthwise and scrape the seeds out with a spoon.
Then cut the cucumber into half cm slices. Put them in a sieve, season with salt and leave to sweat for a couple of hours.
Dry-fry the sesame seeds (i.e. without oil) and put them aside.
Peel and chop the ginger and the garlic then, using a pestle and mortal, crush into a course paste.
Mix the vinegar with the sugar until clear. Add the oil and garlic paste, toss well.
Wipe the cucumber pieces with kitchen towel and scatter them into a serving dish. Sprinkle the sesame seeds and pour the sauce over.
Cut the nori sheets into 1 x 2-cm strips, add these to the cucumber. Mix well.
Just before serving sprinkle with chopped coriander leaves.