Shaved Cauliflower and Radicchio Salad

Name: Shaved Cauliflower and Radicchio Salad
Ingredients: 1/2 head of a 1-pound cauliflower, cored, cut into florets; 1/2 head of a 6-ounce radicchio, cored, quartered lengthwise; 6 inner celery stalks with leaves; 1/4 cup thinly sliced chives; 1/4 cup flat-leaf parsley leaves; 1 lemon; 2 teaspoons Dijon mustard; 1/4 cup walnut oil; Kosher salt, freshly ground pepper; 1 ripe Bosc pear; 1/4 cup coarsely chopped walnuts, toasted if desired; Ingredient info: Walnut oil is available at some supermarkets, natural and specialty foods stores, and at latourangelle.com.