Ingredients 
4 pounds russet potatoes (about 8)
Coarse salt and freshly ground pepper
3 tablespoons cider vinegar
3 large eggs
1 cup mayonnaise
1/2 teaspoon celery seed
1 teaspoon dry mustard
2 tablespoons hot water, plus more if needed
3 stalks celery, cut into 1/4-inch dice (3/4 cup)
1 red bell pepper, stemmed, seeded, and cut into
1/4-inch dice (1/2 cup)
1 medium onion, finely diced (1/2 cup)
10 cornichons, cut into 1/4-inch dice (1/4 cup)
3 scallions, thinly sliced (1/2 cup)
2 tablespoons freshly chopped flat-leaf parsley
1 teaspoon paprika
Directions
1. Place potatoes in a large pot with enough water to cover by several inches. Bring to a boil over high heat, add 1 tablespoon salt, and reduce to a gentle boil. Cook until potatoes are tender when pierced with a knife, about 25 minutes. Drain into a colander. Using paper towels or gloves to protect your hands, peel potatoes, and cut into 1-inch dice while still hot. Drizzle with vinegar; set aside.
2. Place eggs in a small pan with enough water to cover by 1 inch, and place over medium-high heat. When water comes to a boil, turn off heat, cover, and let stand for 13 minutes. Drain, and place in a bowl with cold water to cover. When cold, peel eggs. Chop 2 into 1/4-inch dice. Slice the third egg into 1/4-inch-thick rounds, and set aside for garnish.
3. Combine chopped eggs, mayonnaise, celery seed, mustard, 2 teaspoons salt, and 1/2 teaspoon black pepper in a large bowl; whisk to combine. Thin mixture with hot water, if desired. Stir in reserved potatoes, celery, red pepper, onion, cornichons, scallions, and chopped parsley. Chill for 30 minutes before serving. Garnish with paprika and reserved hard-boiled egg rounds. Serves 10 to 12
Source: Martha Stewart Living