Cook your potatoes unpeeled. They are cooked when inserting a sharp knife you don't feel any resistance.

Drain your potatoes and peel them while still hot.

Slice your potatoes directly into the serving bowl.

Dice your onion. I like the onion smaller, about the size of 1/10 inch (2 mm).

In a small bowl mix oil, vinegar, mustard, salt, pepper and tarragon.

Bring the stock to a boil.

Pour the hot stock over the onions. Stir.

Pour the stock and onions over the potatoes. Toss it a few times.

Pour the oil dressing over your salad. Toss again a few times.

Cover with plastic wrap and let it chill in the fridge for at least 2 hours, overnight is better.