Step 1

Bring an inch or two of water to a boil in a large pot fitted with a steamer basket. Add potatoes, cover and cook until tender, 10 to 12 minutes. Remove the potatoes from the pot.

Step 2

Meanwhile, whisk mayonnaise, vinegar, mustard, salt and pepper together in a large bowl. Add celery, scallions and the cooked potatoes. Stir to coat. Chill until cool or cold, at least 1 hour.