Japanese cucumbers are slender, thin-skinned and almost seedless; one weighs about 100 g. If you can't find one, a mini cucumber (Lebanese type) works well; with an English cucumber, use about 100 g and remove the seeds. Cut the slices 1 to 2 mm thick, ideally on a mandoline, so they are even.Variations: slices of cooked octopus, cut on the diagonal, can be added to the cucumber with the same dressing; a little julienned ginger or finely shredded shiso, added at the end, brings freshness. Cooked shrimp or surimi sticks (kani) are also common.