Preparation Put watercress and frisée in a large serving bowl. Whisk together oil, vinegar, shallot, 1/4 teaspoon salt, and 1/8 teaspoon pepper in a small bowl. Julienne apple lengthwise using slicer until you reach core, then rotate and continue. Add to greens. Julienne celery root and add to greens. Toss salad with vinaigrette and salt and pepper to taste.