New Potato and Radish Salad with Mustard-Dill Vinaigrette

Cornichons are tart, salty and full of pickled flavor. Along with the mustard, they add zip to the tender waxy potatoes and crunchy radishes and celery in this simple salad. A spoonful of creme fraiche on individual servings tempers the salad's tanginess and adds a luxurious touch.