Take the middle part of Daikon, peel and cut into ¾-inch thick rounds. You’ll have about 6 to 8 depending on the size of the daikon. Fill a pot with water, put Daikon in side. Boil and turn down the heat. Ladle out a little of the water into a small bowl, dissolve miso in the water, then pour back to the pot. Simmer for 15 to 20 minutes. While you are waiting for the Daikon to be cooked, mix soy sauce, Dijon mustard and Mayonnaise. Take out the Daikon rounds and place in a serving plate. Spread some sauce on each round and garnish with some green onions.