Place potatoes and 1 tablespoon salt in large pot and cover with cold water until water level is 1 inch above potatoes. Set over medium-high heat until boiling. Reduce heat to medium and simmer until a paring knife can be inserted into potatoes with no resistance, 10-15 minutes. Strain potatoes and set aside.

While pototoes are cooking, place bacon in a large skillet and cook over medium-high heat until crisp. Remove bacon to a paper towel lined plate, leaving as much rendered fat in the pan as possible. Pour out all but about 3 tablespoons of fat from pan.

Add onions to pan with bacon fat and cook over medium heat until lightly browned, about 5 minutes. Remove from heat and set aside.

In a small bowl, whisk together vinegar, sugar, mustard, 2 teaspoons of salt, and pepper to make the dressing.

Place potatoes, bacon, onions, parsley, and chives in a large bowl. Add dressing and toss gently to combine. Let sit for 10 to 15 minutes to allow flavors to meld, then serve immediately while still warm.