Cook the potatoes: Place the unpeeled potatoes in a large pot of salted water. Bring to a boil and cook for 15-20 minutes until tender but still firm.

Cool and peel: Drain the potatoes and let them cool slightly. Peel them while still warm, then slice into 1/4-inch thick rounds.

Prepare the dressing: In a small bowl, whisk together vinegar, vegetable broth, Dijon mustard, sugar, salt, and black pepper. Slowly drizzle in the oil while whisking to emulsify.

Combine ingredients: Place the warm potato slices in a large bowl. Add the diced red onion and pour the dressing over them. Gently toss to coat evenly.

Let it rest: Allow the salad to sit for at least 15 minutes to absorb the flavors. Stir occasionally to redistribute the dressing.

Add herbs: Just before serving, sprinkle with fresh chives and parsley. Adjust seasoning if needed and serve slightly warm or at room temperature.