Boil potatoes in big pot of water until cook. If potatoes are very large, cut them in half. Drain and cool completely. Then remove skin and cut into 1" cubes.
Combine the celery, onion and capsicum with the cubed potatoes in a large mixing bowl.
In another bowl, add all the ingredients for the dressing and mix well. Add salt and pepper to taste.
Pour the dressing over the salad and toss to combine. Transfer to a serving bowl. Garnish with spring onion.
Cover salad bowl with clingwrap and place into refrigerator for about an hour. Serve cold.
