Boil unpeeled potatoes in salted water until just tender (about 20–25 minutes depending on size).
A knife should go through with slight resistance. Drain and let them cool until just warm enough to handle.
Peel the potatoes while still warm (the skins should slip off easily) and slice them into thin rounds. Place them in a large mixing bowl.
In a small pan, cook the bacon until crisp.
Remove the bacon and add the onion.
Sauté the diced onion until just soft but not browned.
Add warm broth, vinegar, mustard, sugar, oil, salt, and pepper.
Simmer for 1–2 minutes to meld the flavors.
Pour the warm dressing over the warm sliced potatoes. Gently fold with a spatula or spoon, try not to break the slices. Let it sit for at least 30 minutes so the potatoes absorb the dressing.
Add the chopped herbs and bacon, and adjust seasoning.
Serve slightly warm or at room temperature.