Peel and cut the cucumbers in half lengthwise, remove the seeds with a teaspoon and cut the cucumber into thin slices slightly on the bias.
Cut the shallot into very fine julienne strips and soak in water for 20 minutes,
drain and cool.
For the Sauce:
Mix all ingredients in a bowl. Set aside. Dissolve the dashi granules in a tablespoon of hot water and add to the sauce. Chill.
Cook the noodles for 2 minutes in boiling water, remove and refresh in cold water. Mix the noodles with the prawns, cucumber, wakame and shallot with the dressing.
