Wash the cucumber, cut it in half lengthwise and scrape the seeds out with a small spoon. Cut the cucumber into 1 cm thick half moons, then cut them in half again.
Wash, trim, then thinly slice the spring onions. Wash, trim and slice the radishes or cut them into small chunks.
Scatter the chopped vegetables into a bowl.
Mix the soy sauce, ginger, sesame oil and rice vinegar. Add the ginger and garlic. Taste it and add some sugar or honey to your liking. Taste it again and adjust the flavours.
Pour the dressing over the vegetables and add half of the sesame seeds. Toss well. Rest for about 10 minutes, then add the remaining sesame seeds and the cress, just before serving.