Place potatoes and 1 tablespoon salt in large saucepan and cover potatoes with water by 1 inch. Bring to boil over high heat; reduce heat to medium; and cook until potatoes are fork-tender, about 13 minutes.
Drain potatoes in colander, then transfer them to rimmed baking sheet and let cool completely, about 30 minutes.
Meanwhile, combine onion, oil, horseradish, lemon juice, mustard, pepper, and salt in large bowl; set aside while potatoes cool.
Add cornichons, parsley, dill, and potatoes to onion mixture and toss to thoroughly combine. Let sit for 20 minutes for flavors to blend. Season with salt and pepper to taste. Serve. (Potato salad an be refrigerated for up to 2 days. Let come to room temperature before serving.
Assemble, Stovetop
2024