- In a blender, yogurt, lemon juice, vinegar, celery seed, dillweed, dry mustard, and white pepper until smooth.
- Chill for 1 hour.
- Scrub potatoes; boil in jackets until tender.
- Cool; peel.Cut into ½-inch cubes.
- Add celery, green onion, and parsley.
- Pour chilled mixture over vegetables; mix well.
- Chill at least 30 minutes before serving.