Boil potatoes for 18 minutes. Finely dice the onion, bring to the boil in the broth with vinegar, keep warm. Peel the potatoes, cut into slices in the stock while still warm, season, let stand for at least 30 minutes until the liquid is absorbed.
Slice the gherkins, roll the chives, dice the bacon and fry until crispy. Mix the mayonnaise with the cream and 6 tablespoons of the liquid from the gherkins.
Mix everything and let it steep for 2 hours, season again to taste.