Most potato salads look and taste better when made with low-starch red boiling potatoes. For Classic American-Style Potato Salad, you can use any size of this variety, but the small new potatoes cook 10 to 15 minutes faster than the larger ones. Choose potatoes that are all roughly the same size, if possible, so they cook in the same time.
Place potatoes in a pot with water to cover. Bring to a boil, cover and simmer, stirring to ensure even cooking, until a thin-bladed paring knife or a metal skewer inserted into a potato can be removed with no resistance, 25 to 30 minutes. Drain, rinse under cold water and drain again. Cool slightly.
Cut warm potatoes into 3/4-inch dice with a serrated knife. Layer them in a bowl, seasoning with vinegar, salt and pepper as you go. Cut eggs, celery and pickle in 1/4-inch dice and thinly slice scallions. Add to potatoes, along with parsley. Stir in mayonnaise and mustard until everything is combined. Chill, covered, before serving.
Per Serving: 291 calories; protein 6.5g; carbohydrates 28.8g; fat 17.3g; cholesterol 99.5mg; sodium 549.9mg.