Cook scrubbed, unpeeled potatoes in boiling water until tender but still slightly firm, and allow to cool.
Hard-boil eggs; cool and remove shells.
In a large bowl mix mayonnaise, sour cream or heavy cream, salt, sugar, and mustard. Now taste it. Some mayonnaise needs a little extra salt, sugar, or vinegar. The flavors will be strong, but this gives a sense of the flavor balance.
Stir in onion and celery. Quarter and slice eggs and add. Peel and slice potatoes into approximately 12-inch pieces and add. Gently fold all ingredients together.
Cover and refrigerate at least 3 hours to allow flavors to blend.