In 3- to 4-quart saucepan, cook sliced potatoes in small amount of boiling water about 10 minutes or until tender; drain well. Meanwhile, cut eggs into eighths.
In large bowl, mix warm potatoes, eggs, fennel, celery and onion. In small bowl, mix dressing ingredients. Spoon dressing over salad; toss gently. Cover; refrigerate 1 to 2 hours or until chilled. Garnish with fennel leaves if desired.