Wash the potatoes thoroughly or scrub them with a vegetable brush. Boil in water for about 20 minutes. Pour off, rinse with cold water and let cool.
Peel the onions. Finely dice 1 onion, halve the others and cut into thin rings. Heat 1 tablespoon of oil. Fry the onion cubes in it. Add vinegar, 1⁄8 l water and stock. Bring to the boil and simmer for about 2 minutes.
Season with salt, pepper and 1 pinch of sugar.
Halve or quarter the potatoes lengthwise. Pour hot marinade immediately over the potatoes and leave to stand for about 30 minutes.
Wash all herbs, shake dry, pluck off the leaves and chop them coarsely. Mix mustard, honey and 5 tablespoons of oil. Mix the herbs, onion strips and mustard dressing with the potatoes. Season potato salad with salt and pepper.