Wash the potatoes thoroughly, cover and cook in boiling water for about 20 minutes. Drain, rinse with cold water and let it evaporate a little. Peel the potatoes and cut them into thin slices while still warm.
In the meantime peel and finely dice the onions. Fry in 2 tablespoons of hot oil. Stir in mustard, vinegar and stock, bring to the boil briefly. Season with salt and pepper. Mix the hot vinaigrette with the potatoes. Minimum.
Leave to soak for 30 minutes.
Wash the chives, shake dry and cut into small rolls. Add 3 tablespoons of oil and chives to the salad. Season potato salad with salt and pepper.