Cut the green top off the fennel. Then, using a sharp knife, cut the bulbs in half and cut out the triangular-shaped core in each half. Using a knife or a mandolin, thinly slice the fennel.
Cut the tough green top off the leek, remove the bottom/root part of the leak and slice the white part only (be sure to thoroughly wash the leek.
Cut the tip off the asparagus and cut the stem into 2-inch pieces on a diagonal, discarding the bottom piece of the stock (where it's woody.) Add 2-inch pieces and tops to the salad.
In a large bowl or platter, combine the sliced fennel, leeks, and asparagus. Top with shaved Parmesan Reggiano cheese.
In a small jar or bowl, whisk together the lemon juice from one fresh lemon – about 1/4 cup, the olive oil, fresh thyme, and salt and pepper. Then drizzle over the fennel, asparagus, leek, and Parmesan. Toss to evenly distribute the dressing.
Garnish with slivered almonds or pignoli nuts. Serve immediately.
