Place the potatoes in a large saucepan and cover by at least an inch with cold water, and add a large pinch of salt. Bring to a boil. Reduce heat to medium and cook potatoes until they are still firm but can be pierced easily with a fork. Drain and transfer to a bowl. Sprinkle the potatoes wth the cider vinegar and toss gently. Let cool.
While the potatoes are cooking, place the eggs in a medium saucepan and cover by at least an inch of water. Bring to a boil and remove from the heat. Cover the pot and let it sit for 11-12 minutes. Drain and transfer the eggs to a bowl of cold water to stop the cooking. Peel and chop the eggs.
While the potatoes and eggs are cooking, place the chopped bacon in a cold skillet and turn heat to medium. Cook until browned and crispy and drain on paper towels. Transfer 1 tablespoon of the bacon grease to a large bowl.
To the bacon grease, add the mayonnaise, Dijon mustard, relish, Old Bay, salt, and pepper. Whisk to combine.
To the dressing, add the potatoes, celery, onion, chives and parsley, and toss gently to combine. Fold in the eggs and bacon. Season to taste with additional salt and pepper.