Place the Waxy Potatoes in a large pot, cover with cold water, add a pinch of Salt, and bring to a boil. Cook until just tender when pierced with a fork, about 20–25 minutes depending on size.
While the potatoes cook, finely slice the Yellow Onion. In a small saucepan, warm the Sunflower Oil over medium heat and gently soften the onion for 2–3 minutes until translucent but not browned.
Add the Beef Broth, White Wine Vinegar, Mild Mustard, and Sugar to the pan with the onions. Stir well, bring to a gentle simmer for 2–3 minutes to meld the flavors, then season with freshly ground Black Pepper and additional Salt to taste.
Drain the potatoes, let them cool just enough to handle, then peel while still warm and slice them about 3–5 mm thick. Place the warm potato slices in a shallow bowl or serving dish so they can soak up the dressing.
Pour the hot broth‑onion dressing evenly over the warm potato slices so the potatoes absorb the liquid. Gently toss or turn the slices with a fork to coat without breaking them.
Let the salad rest at least 10 minutes (or up to 1 hour at room temperature) so the flavors develop; taste and adjust seasoning with more Salt, Black Pepper, or a splash of White Wine Vinegar if desired.
Just before serving, sprinkle chopped Chives over the salad for a fresh, oniony finish. Serve warm or at room temperature alongside sausages, schnitzel, or as part of a buffet.
