2 lbs red or other waxy potatoes

1 stalk celery, diced

2 tbsp finely snipped fresh chives or 2 scallions, minced or 2 tbsp minced red onion

1/4 cup minced fresh parsley

¾ cup mayonnaise, or a little more if needed

2 tbsp milk or red wine vinegar

1 pinch salt

1 pinch black pepper