Wash and cut 2 lb potatoes into 1-inch cubes
Boil potatoes in salted water until tender, about 12–15 minutes
Drain potatoes and let cool until just warm
Chop 1/2 to 1 cup celery (optional)
Chop 1/2 medium onion (optional)
Dice 4 hard-boiled eggs (optional)
In a bowl, mix 1 cup mayonnaise, 2–3 tbsp yellow mustard, 2–3 tbsp pickle relish, 1–2 tbsp vinegar or lemon juice, 1–2 tbsp chopped pickles (optional), 1 tsp salt, and 1/2 tsp black pepper
Add celery, onion, and eggs to the dressing and stir
Add cooled potatoes to the bowl and gently fold to combine
Taste and adjust salt, pepper, mustard, and vinegar/lemon
Cover and refrigerate at least 1 hour before serving
Garnish with chopped parsley or paprika (optional)