Thoroughly wash the kale leaves. Add 1/2 tbsp lime juice and gently massage the leaves until they have softened.
Prepare the dressing: add sugar to the hot water and stir to dissolve. Whisk in the rest of the dressing ingredients. Taste and adjust for salt, sweet or acid.
Use 1/2 of the dressing to pour over the cucumbers. Let them sit for 5-10 minutes to take in the flavours of the dressing. (You can skip this step if you don't have the time)
Add the cucumbers, kale and most of the coriander leaves to a serving bowl and give it a gentle mix.
Drizzle with the rest of the dressing and top with sesame seeds and the remaining coriander leaves.
Notes
You can swap fish sauce with soy sauce for a vegan version.