How to Make It
Using a mandoline, thinly slice the fennel and transfer it to a large bowl. Thinly slice the cremini mushrooms and set aside.
In a small bowl, whisk the olive oil with the lemon juice. Season generously with salt and pepper. Pour all but 1 tablespoon of the dressing over the fennel; season with salt and pepper and toss to coat.
Mound the sliced fennel on plates and top with the sliced cremini. Shave Parmesan over the salad. Drizzle with the remaining 1 tablespoon of dressing and the truffle oil and serve.
White truffle oil is available at most specialty food stores or through Urbani Truffles at urbanitrufflesonline.com.