Place potatoes in a large saucepan; add water to cover. Bring to a boil. Reduce heat; cook, uncovered, 10-15 minutes or until tender. Remove potatoes with a slotted spoon; cool. Return water to a boil. Add asparagus; cook, uncovered, 2-3 minutes or just until crisp-tender. Remove asparagus and immediately drop into ice water. Drain and pat dry.
Transfer potatoes and asparagus to a large bowl; add radishes, green onions and herbs. In a small bowl, whisk vinaigrette ingredients until blended. Pour over potato mixture; toss gently to coat. Serve at room temperature or chilled. Stir before serving.