Schwäbischer Kartoffelsalat (swabian potato salad)

For 2-3 persons:
1 kg Waxy potatoes (Sieglinde, Cilena, Nicola, Selma...)
1 Medium-sized white onion (about 200 g)
1/2 TBS Dijon mustard
230 ml Fresh vegetable stock or cattle bouillon
4 TBS Salad oil (sunflower, peanut or corn oil)
3,5 TBS High quality white wine vinegar
1 TSP Salt and a pinch black pepper
15 g Chopped chives
1 TSP Butter

Preparation: The correct kind of potatoes is very essential! First, boil the peeled potatoes in salty water until there are done (test with a fork after 10 minutes). Than let the potatoes cool to room temperature and grate them into 2-4 mm thick slices. Dice the onions into small pieces and sauté in little dripping until onions are soft but not browned. Now mix the warm bouillon (or stock) with mustard and vinegar (free from lumps) and melt the butter in the warm mixture. Than add salt, pepper and the onions and pour everyting over the sliced potatoes. Mingle everything well (but carefully) and let rest for 30 minutes. Now add the oil, mingle well and let rest for minimum 2 hours. Decorate with chopped chives and serve. It's a side dish, mostly for meat, sausages or Maultaschen.