In a large bowl toss together shredded cabbage, carrots, cucumber, radish, and green onion.
To make the dressing, place all ingredients into a food processor or blender. Pulse until smooth adding in additional water if the dressing is too thick.
Use about 2/3 cup dressing, toss in the salad. Top with chopped hazelnuts. Refrigerate until ready to serve (best enjoyed within 1-2 days). Save the rest of the dressing for another use, it will store well in the fridge for up to 3 weeks.