I met Fred about nine years ago and each time his mother visits us from Philadelphia, he requests she make this German Potato Salad along with her Philly Style Mac and Cheese. At first, as a good Mid-Western girl, I was appalled that this didn't have any mayo in it. But over the years I've learned more about what's really healthy and this salad has won a place in my favorites. I love the simplicity of olive oil, vinegar, salt and onions. Very easy. This salad sits out on the counter overnight to develop the flavor and truly it only tastes its best at room temperature where the oil stays golden.
Boil potatoes with skin on in a large pot of water. Start checking them for doneness at about 10 minutes. You want the potatoes to give to the tines of a fork but not be so soft that pieces break off. Pull the potatoes out of the water and set on a rack or towel to cool a bit. When you can handle them without burning yourself, peel away the skins. Slice the potatoes while still very warm into a large glass or ceramic bowl (do not use metal or wood, as they affect the taste).
Add your minced onion to the warm potatoes, then pour the oil over the potatoes and the vinegar on around the outside of the potatoes so it pools to the bottom. Fold all this gently, so the oil, vinegar and onion are distributed evenly. Add salt and pepper to taste. Depending on the amount of potatoes, you may need to increase your oil and vinegar. This salad is meant to be wet. Keep your oil 1/3 more than your vinegar (so if you add 3 Tblsp of oil, then add 2 Tblsp vinegar). Cover and leave out overnight so the oil and vinegar soak into the potatoes. Refrigerate if you must but before serving, let it sit to room temperature. You can also add chopped bacon.