How to Make It
Fill a large saucepan with 1 inch of water and fit with a steamer basket; bring the water to a boil. Place the potatoes in the basket, cover, and steam until tender, 12 to 14 minutes; drain.
Meanwhile, in a medium bowl, mix together the herbs, scallions, oil, mustard, vinegar, ½ teaspoon salt, and ¼ teaspoon pepper. Add the cooked potatoes and toss to combine.