Love this classic potato salad. It comes from Sandi, of the Whistle Stop Cafe, in Irondale, Alabama. I made it exactly like the recipe except, I used only about a quarter of an onion, chopped fine.
Southern Mustard Potato Salad
1-2 pounds potatoes
4-5 hard boiled eggs
1 sweet onion, diced
1/2 cup diced celery
1/4 cup pickle relish
3 Tbs spicy mustard
1/2 cup mayo
Clean potatoes then boil them whole. Once tender, 15-20 minutes, remove from heat and allow to cool. Dice onion and celery. Dice potatoes into large chunks.
In another bowl whisk together mayo, mustard and pickle relish. Add kosher salt and fresh ground pepper to taste. Stir all ingredients together. Finally, peel and slice the hard boiled eggs and stir those in as well. Serve warm or cold.

It tastes like great diner potato salad. Just perfect! Thanks, Sandi.