1. Place the potatoes in a medium saucepan; cover with cold water. Bring to a boil. Reduce heat, and simmer 10 minutes or until tender. Drain and cool.
2. Combine yogurt and next 3 ingredients (through salt), stirring with a whisk.
3. Place cooled potatoes in a large bowl. Add carrots, 5 tablespoons green onions, celery, and yogurt mixture; toss gently to combine. Sprinkle with remaining 3 tablespoons green onions and cashews. Serve chilled.