Thinly slice the fennel across the bulb with a sharp knife or mandoline. To slice the pears, hold upright on the bench and thinly slice down each cheek to keep the natural shape. Place fennel and pear in a bowl.

Whisk oil and lemon juice together in a bowl, season, then lighten with a dash of water. Toss with fennel and pear, divide among plates, then scatter with chunks of parmesan, walnuts and fennel fronds.