Cook the potatoes: Place whole, unpeeled potatoes in a pot, cover with cold water, and add a generous pinch of salt. Bring to a simmer and cook until just tender when pierced with a knife, about 15–20 minutes depending on size.
Drain and steam-dry: Drain the potatoes and let them sit uncovered for 5 minutes to release excess moisture.
This helps them absorb the dressing later.
Cook the bacon: While the potatoes cool slightly, cook bacon in a large skillet over medium heat until crisp. Transfer bacon to a plate, leaving 1–2 tablespoons of fat in the pan.
Soften the onion: Add the diced onion to the bacon fat and cook over medium heat until translucent and lightly golden, 3–4 minutes. Stir often so it doesn’t brown too much.
Build the dressing: Pour in the broth and vinegar, then whisk in mustard, sugar, salt, and pepper.
Bring to a gentle simmer for 1–2 minutes to meld flavors. Taste and adjust—aim for bright and balanced.
Slice the potatoes warm: Peel the potatoes while still warm if desired (skins slip off easily), then slice into 1/4-inch rounds. Work carefully so they don’t crumble.
Combine and soak: Place the warm potato slices in a large bowl.
Pour the hot dressing over them and gently toss. The potatoes should look glossy and slightly thirsty—add a splash more broth if needed.
Add fat for body: Stir in neutral oil (or a mix of oil and 1–2 tablespoons reserved bacon fat) to create a silky finish. Fold in the crisp bacon, parsley, and chives.
Add optional pickle or capers if using.
Rest and taste: Let the salad sit for 10–15 minutes. Taste again and adjust with more vinegar, salt, or a pinch of sugar to hit that sweet-sour balance.
Serve warm: Serve warm or at room temperature. If the salad looks dry, loosen with a splash of warm broth or a drizzle of oil just before serving.