Step 1

To prepare the leeks, cut off the tops just after the lightest green part (you can use the dark green parts, well washed, to make soup stock; otherwise, discard). Cut off the coarsely bristled end and discard as well.

Step 2

Cut the remaining white and palest green stalk in half lengthwise, then into 1/4-inch-thick half-rings. Place the half-rings in a colander and run water over them, separating them as you do, until completely clean. (Tip: If the leeks are very sandy, first put the slices into a bowl of water and swish around to loosen before transferring to a colander to complete the rinsing).

Step 3

Trim the stalks away from the fennel bulb. Quarter and slice the bulbs, then slice the stalks thinly. Reserve the delicate leaves.

Step 4

Heat the optional oil, wine, and lemon juice in a large skillet. Add the leeks, fennel, and mushrooms, and sauté over medium heat, stirring frequently, until the leeks are wilted and the fennel is tender-crisp, about 12 to 15 minutes. Add tiny amounts of water if needed to keep the skillet moist.

Step 5

When the vegetables are done to your liking, stir in the parsley and nuts. Season with salt and pepper.

Step 6

Scatter the reserved fennel leaves over the top (or save to garnish individual servings) and serve at once, straight from the skillet.