How to Make It
In a large pot, cover the potatoes with water. Add a large pinch of salt and bring to a boil. Simmer over moderately high heat until the potatoes are tender, about 20 minutes. Drain well. Transfer the potatoes to a large bowl and let cool to room temperature.
Meanwhile, in a food processor, combine the celery with the onion, olives, cornichons and capers and process until finely minced. Add the mayonnaise, mustard and lemon juice and pulse until blended.
Add the dressing and the parsley to the cooled potatoes and mix well. Season with salt, pepper and hot sauce. Cover and refrigerate until ready to serve.