Cook jacket potatoes for 15-20 minutes (depending on size). Make sure the potatoes are tender, but not too soft, so they keep their shape when slicing.
Drain the cooked potatoes and let them cool down a bit for 15 minutes. Peel the skin off and slice them into half cm wide slices.
Chop the onions.
Prepare your dressing
Heat up your broth in a small pot. When it starts to boil, turn the heat off, and add the onions, as well as white wine vinegar, sugar, mustard, salt and pepper.
Pour the dressing over the potatoes and let it rest in the fridge for at least 1 hour.
Before serving add the oil and mix the salad well.
Correct the seasoning. Add nutmeg if you like!
Notes
If you are making potato salad one day ahead I would prepare more dressing, as the potatoes will soak most of it.