Add potatoes to a large pot and cover with cold water.
Add a generous pinch of salt to the water.
Bring to a boil, then lower to a steady simmer.
Cook 10 to 14 minutes, until fork-tender.
Drain the potatoes well and keep them warm.
Cook chopped bacon in a skillet until crisp.
Move bacon to a paper towel-lined plate.
Keep 2 tablespoons bacon drippings in the skillet.
Add onion and cook 3 to 4 minutes.
Stir in vinegar, broth, mustard, sugar, salt, and pepper.
Simmer 1 to 2 minutes, while stirring.
Pour warm dressing over the warm potatoes.
Fold gently until the potatoes look coated.
Add bacon and parsley, then toss lightly.
Taste and add more salt or pepper if needed.
Serve it warm, not blazing hot.