This is a terrific salad to serve with a rich entrée: tart, refreshing, and a great palate cleanser. The parsley and mint stand in as greens instead of lettuce for a lighter, more brightly flavored dish. Use a mandoline or hand-held vegetable slicer to make quick work of the slicing and julienne steps.
Thinly slice the fennel and transfer to a medium-size bowl. Add the julienned apples, parsley, mint, hazelnuts, and scallions, and toss to combine.
Whisk the lemon juice and hazelnut oil in a small bowl and season to taste with salt and pepper. Add the dressing to the fennel mixture and toss to combine.
The salad can be made 2 hours ahead of serving and stored in the refrigerator, covered.