|10||medium Yukon Gold or Yellow Finn potatoes, scrubbed|
|2||tablespoons cider vinegar|
|1/2||teaspoon salt, or to taste|
|1/4||teaspoon pepper, or to taste|
|1||tablespoon white wine vinegar|
|1||teaspoon Dijon mustard|
|2||tablespoons olive oil|
|6||scallions (white ends only), coarsely chopped|
|3||stalks celery, halved lengthwise and thinly sliced on a diagonal|
|Handful of fresh parsley, coarsely chopped|
1. Set a steamer insert in a large saucepan. Add enough water to come up to the bottom of the steamer. Bring to a boil. Add the potatoes, cover, and steam for 20 minutes or until tender. Add more water to the pan during cooking, if necessary.
2. With a slotted spoon, transfer the potatoes to a cutting board. While they are hot, halve lengthwise, then slice thickly. Transfer to a bowl. Sprinkle with cider vinegar, salt, and pepper. Stir gently with a rubber spatula to turn the potatoes. Set aside until cool.
3. In a small bowl, whisk together the mayonnaise, wine vinegar, and mustard. Slowly whisk in the oil until the dressing emulsifies.
4. Pour the dressing over the potatoes. Add the scallions, celery, and parsley. Stir gently but thoroughly. Taste for seasoning and add more salt and pepper, if you like. Cover and refrigerate for up to 2 hours.