Shaved Apple Fennel Salad

Name: Shaved Apple Fennel Salad
Ingredients: 1/4 cup extra-virgin olive oil; 2 Tbsp. sherry vinegar; 2 tsp. whole-grain mustard; 2 tsp. pure maple syrup; 1 1/2 tsp. finely chopped shallot (from 1 shallot); 1 1/4 tsp. kosher salt; 1/4 tsp. freshly ground black pepper; 1 large bulb fennel, trimmed, cored, and very thinly sliced (about 2 1/2 cups), fronds reserved for garnish; 1 medium Granny Smith, Golden Delicious, or Mutsu apple, cored, quartered, and very thinly shaved, preferably using a mandoline (about 1 3/4 cups); 1 medium Honeycrisp, Fuji, or Braeburn apple, cored, quartered, and very thinly shaved, preferably using a mandoline (about 1 3/4 cups); 2 medium stalks celery, very thinly sliced (3/4 cup); 1/2 cup chopped toasted pecans