Place the noodles, radishes and cucumber into three separate bowls and transfer to the fridge to chill for at least one hour.
For the dressing, combine all of the dressing ingredients together in a small bowl.
To serve, transfer the noodles to a large serving dish, layer with some radish and cucumber and scatter over the black sesame seeds. Spoon the dressing over the noodles and garnish with coriander sprigs. Serve immediately.