Halve the cucumber lengthwise. Using a teaspoon, scoop out and discard the seeds. Cut the cucumber into thin slices and place in the salted water for at least 10 minutes.

When ready to serve, drain the cucumber slices and place in a serving dish with the spring onion, garlic if using, vinegar and chilli powder. Crush the toasted sesame seeds and sugar in a pestle and mortar (or blender), add to the salad and mix well.