Place the potatoes and 1 tablespoon of the salt in a large saucepan.
Cover with 1-inch cool water; bring to a boil over high heat.
Reduce the heat to medium; simmer until the potatoes are easily pierced with a knife; 30 to 35 minutes.
While potatoes are boiling, place the bacon in a large skillet, over medium heat, and cook until the fat begins to render; about 8 minutes.
Add the onion; cook until the onion and bacon brown and the bacon is crisp; 13 to 15 minutes.
Use a slotted spoon to transfer the bacon and onions to a paper towel-lined plate.
Measure the remaining fat in the pan; if there is less than 3 tablespoons, add enough oil to equal 3 tablespoons.
When cooked, remove the potatoes from the stove and, using a colander, drain; rinse under cold water until they are cool enough to handle.
While not necessary for this recipe, if desired, peel potatoes with your fingers or a vegetable peeler; slice into 1/4-inch thick rounds and transfer to a large bowl.
Place the vinegar, sugar, mustard, pepper, remaining 1/2 teaspoon salt and the bacon fat in a jar; cover and shake to combine.
Add the chives, parsley, bacon and onion mixture, and dressing to the sliced potatoes; toss well; set aside for 10 minutes.
Serve warm or at room temperature.
Notes
Refrigerate leftovers in an airtight container for up to 4 days.