Place the potatoes in a large pot with enough cold water to cover and bring to a boil. Add 1 tablespoon salt, reduce heat, and simmer until tender, 15 to 18 minutes. Drain, run under cold water to cool, and cut in half.
Meanwhile, place the eggs in a large saucepan with enough cold water to cover. Bring to a boil. Remove from heat, cover the saucepan, and let stand for 12 minutes. Drain and run under cold water to cool. Peel and roughly chop.
In a large bowl, whisk together the mayonnaise, yogurt, lemon juice, mustard, shallots, ½ teaspoon salt, and ¼ teaspoon pepper until smooth.
Add the potatoes, eggs, watercress, and chives and toss to coat.
You May Like
Real Simple Newsletters
Get tips, inspiration and special offers delivered to your inbox.