For the potato salad, boil the potatoes until soft, peel and cut into thin slices. Allow to cool a little. Generously pour oil over the cooled potatoes, salt, pepper and stir well.
In a 250 ml jar or mug for the marinade, add a teaspoon of granulated sugar. Then fill about 1/3 of the jar with tarragon mustard and pour a dash of vinegar over it.
Fill the glass with water and stir the marinade well. Pour the marinade over the sliced potatoes and finally add 1/2 bunch of chopped chives.
Stir everything well and let it sit in the refrigerator for a few hours.