Combine potatoes, onions, radishes and hard-cooked eggs.
Blend remaining ingredients; mix lightly with potato mixture. Chill.
Serve in salad bowl lined with endive or leaf lettuce, and garnish with hard-cooked eggs (we cut them with an egg slicer) and radish-pineapples (tuck 1″ lengths of sliced green onion tops in holes cut in radishes).