Growing up my mother made a knockout pareve potato salad - Just potatoes, diced scallions, grated carrots, mayo, sugar, salt and white vinegar. It was never runny on the second day and it didn't get more and more tasteless as the days wore on. I can't seem to replicate it anymore and Mom forgot any tricks she might have utilized. I've tried what seems like all the variations ie putting the dressing on warm or hot or cold potatoes, stirring in the mayo at the last minute, blanching the other ingredients, etc etc to no avail. It tastes great right after you make it but the quality decreases rapidly thereafter. Any ideas?