In a small bowl, whisk vinegar, mustard, sugar, salt, and pepper.
4 Pour hot broth into the mixture and whisk.
Combine
5 Place warm potato slices in a large bowl.
6 Pour dressing over potatoes, toss gently. The warm potatoes will absorb the liquid.
Finish
7 Let sit 30 minutes so flavors meld (add more broth if it looks dry).
8 Drizzle with oil, toss again.
9 Sprinkle parsley on top before serving.