Boil Potatoes: Place potatoes in a large pot and cover with cold water. Add 1 Tablespoon salt. Bring to a boil over medium-high heat, and cook until potatoes are tender but firm, about 10-15 minutes (be careful not to overcook, or the potatoes will get mushy). Drain and set aside.
Cook Bacon: In a large skillet, cook diced bacon over medium heat until crispy, about 8-10 minutes. Remove bacon with a slotted spoon and set aside, leaving bacon drippings in skillet.
Sauté Onion: Add chopped onion to the skillet with bacon drippings. Cook over medium heat until onion is soft and translucent, about 3 minutes.
Make Dressing: Stir in apple cider vinegar, water, granulated sugar, mustard, 1 ½ teaspoons salt, and pepper. Cook, stirring constantly, until mixture is well combined and heated through, about 2 minutes.
Combine Ingredients: Add cooked potatoes and bacon to skillet. Gently toss to coat potatoes with dressing and heat through, about 2-3 minutes.
Add Parsley: Remove skillet from heat and gently stir in chopped parsley.
Serve: Transfer potato salad to a serving dish, garnish with chopped chives, and serve warm.
