Slice the cucumber in half, lengthwise, and scraped out the seeds with a teaspoon. Discard the seeds.
Grate the cucumber halves with a mandoline to get very long, thin ribbons. Pile them up in a few sheets of kitchen paper and squeeze firmly to remove as much water from them as possible
Divide the cucumber noodles into 12 portions.
Separate the white from the brown crab meat in two bowls. (If your crab meat comes mixed together, don't worry, it will still taste delicious)
To the brown meat add the white slices of spring onion and half the minced lemongrass stick. Mix well. Pile the brown meat on top of the cucumber noodles, and top with the white crab meat.
Decorate each cup with the green slices of spring onion, the red chilli slice and a pinch of sesame seeds and keep refrigerated until you are ready to serve.
Mix all the dressing ingredients together in a small bowl and add a little to each Asian crab and lemongrass cup just before serving.