Wash the potatoes and cook for about 20 minutes. Quench and remove the skin. Let the potatoes cool down and cut into slices.
Peel and chop the onions. Fry them in hot oil until they are glassy. Sprinkle with sugar and caramelize briefly. Deglaze with stock and vinegar. Bring marinade to the boil and simmer for about 5 minutes. Season with salt and pepper.
While still hot, pour over the potatoes, mix and leave to stand for at least 1 hour.
Mix crème fraiche and pumpkin seed oil. Also fold into the potatoes. Clean the lamb's lettuce, loosen the leaves, wash and drain well. Arrange potato salad, sprinkle with seeds and lamb's lettuce shortly before serving.