1In 4-quart saucepan, place potatoes and enough water to cover by 1 inch. Heat to boiling; reduce heat to medium. Cook uncovered 10 to 12 minutes. Add asparagus. Cover; cook 2 to 3 minutes longer or until potatoes are tender when pierced with fork and asparagus is crisp-tender. Drain; rinse with cold water.
2In large bowl, mix sour cream, horseradish, half-and-half and salt with whisk until smooth. Add potatoes and asparagus; gently toss to coat. Fold in dill. Cover; refrigerate at least 2 hours before serving.