Directions

1. Place potatoes in a Dutch oven or other 5- to 6-qt. pot and cover with cold water. Add 1 Tbsp. salt. Bring to a boil, then reduce heat and simmer until tender, about 10 minutes. Drain in a colander.
2. While potatoes are simmering, in a large bowl, stir together mayonnaise, Dijon mustard, vinegar, remaining 1/2 tsp. salt, and the pepper. Add onion, celery, and 1/4 cup parsley, and stir.
3. Add drained warm potatoes to dressing and toss to coat. To serve salad right away, set bowl in a larger bowl of ice water and let stand, stirring occasionally, until cool, about 45 minutes. Or cover bowl and refrigerate about 5 hours to cool completely.
4. Sprinkle salad with more parsley. Chill any leftovers up to 2 days and stir before serving.