Grate or shred the daikon, carrots and red pepper. If the red pepper proves difficult to shred, thinly slice it into julienne strips. Place the vegetables and the sesame seeds in a bowl and mix together with your hands.
Put the sesame oil, mirin and vinegar in a small pan and heat gently for 2—3 minutes to blend the flavours. Remove the pan from the heat and allow the mixture to cool a little.
Arrange the salad in a mound in the centre of each of 4 plates and pour the dressing over and around it. Top each salad with finely shredded spring onions, garnish with coriander leaves and serve.