Step 1

Place potatoes in a large saucepan and cover with water. Bring to a boil. Reduce heat; cover and cook until tender, 15-20 minutes. Drain.

Step 2

When cool enough to handle, peel and slice potatoes. Place in a large bowl; add salad dressing and toss gently. Cover and refrigerate for 2 hours.

Step 3

Slice eggs in half; remove yolks and set aside. Chop egg whites; add to potatoes with celery and onions.

Step 4

In a small bowl, combine mayonnaise, sour cream, horseradish, mustard, celery seed and salt. Crumble egg yolks; add to mayonnaise mixture and whisk until blended. Spoon over potatoes; toss gently to coat. Cover and refrigerate at least 2 hours before serving.