• Kosher salt
• 5 pounds red potatoes , peeled and cut into 1-inch cubes
• 1 cup mayonnaise
• 1 cup sour cream
• 1 cup finely chopped green onion
• 1 cup finely chopped flat-leaf parsley
• 1/4 cup finely minced tarragon
• 2 tablespoons white wine vinegar
• 2 tablespoons lime juice
• Freshly ground black pepper

Fill an 8-quart stockpot halfway with water, add 1/4 cup salt; bring to boil over high heat. Add potatoes and cook until fork-tender, about 9 minutes. Rinse under cold water to cool.

Mix next seven ingredients in a large bowl. Season with salt and pepper. Add potatoes, toss with dressing. Cover and chill in the refrigerator at least 1 hour before serving.