While potatoes are warm, pour on the dressing. Chill 2 hours. Add celery and onion. Add the egg whites, chopped. Sieve egg yolks, combine with mayonnaise, sour cream, horseradish, mustard, and celery seed. Chill 2 hours and add diced cucumber.
Contributed by Wesley Pitts Origin: "Wenonah's Pantry", Bryan, TX