Step 1Trim the mushrooms of any dried ends if necessary, then slice them lengthwise as thin as you can. Place the mushrooms in a mixing bowl and season with 1 teaspoon salt, the garlic and red pepper flakes.
Step 2Whisk together the lemon juice and olive oil and add 2 tablespoons of the dressing to the mushrooms. Toss to coat lightly.
Step 3Place the arugula in a large mixing bowl and add just enough of the remaining dressing to coat lightly. Sprinkle with salt to taste and toss well.
Step 4Arrange the arugula on a serving platter and mound the mushrooms on top. Use a vegetable peeler to shave long strips of Parmigiano on top of the mushrooms. Sprinkle with pine nuts and serve immediately.