Creamy, tangy potato salad with eggs and mustard is a family-favorite picnic and cookout side dish. This classic vegetarian recipe feeds a crowd and tastes even better the next day.
Place potatoes in a large pot, cover with cold water, and bring to a boil over medium-high heat. Reduce to medium and simmer until fork-tender, about 18–20 minutes.
While potatoes are boiling, place eggs in a separate saucepan, cover with water, and bring to a boil. Once boiling, turn off the heat and cover for 10 minutes, then cool eggs in ice water and peel.
Drain cooked potatoes, let them cool slightly, and peel if desired. Chop potatoes into 1-inch cubes.
Dice peeled eggs, celery, and red onion. Combine potatoes, eggs, celery, and onion in a large mixing bowl.
In a small bowl, whisk together mayonnaise, mustard, apple cider vinegar, salt, and black pepper until smooth. Pour the dressing over the potato mixture and gently fold to combine. Taste for seasoning and chill at least 1 hour before serving.