Step 1

Preheat oven to 300°F. Line a baking sheet with parchment paper. Spread hazelnuts in an even layer on prepared baking sheet. Bake in preheated oven until very fragrant, about 25 minutes, stirring once after 15 minutes. Let nuts cool slightly, about 5 minutes. Place on a kitchen towel, and rub off skins. Coarsely chop nuts; set aside.

Step 2

Whisk together vinegar, mustard, honey, salt, and pepper in a medium bowl. Gradually whisk in oil in a slow, steady stream until emulsified.

Step 3

Core apple, and cut into quarters. Shave apple quarters into 1/8-inch-thick slices using a mandoline; place in a large bowl. Trim fennel stalks from bulb; coarsely chop fronds to equal 2 tablespoons; discard stalks. Cut bulb into quarters; remove and discard core. Shave bulb into 1/8-inch-thick slices using a mandoline. Add shaved fennel bulb and chopped fronds to apple in bowl.

Step 4

Drizzle fennel mixture with 6 tablespoons dressing; toss to coat. Arrange lettuce on a platter. Top with fennel mixture, cheese, nuts, and remaining dressing.