Sauté mushrooms until lightly browned. Using a slotted spoon, remove to a plate; set aside.

Rinse the skillet out; fill with water to a depth of about 2 inches. Add 1/2 teaspoon of salt. Bring water to a boil; add trimmed asparagus or fiddleheads.

Cook for about 4 to 5 minutes, or just until tender. Bake the pie crust at 375° for 10 minutes to partially cook the crust. Sprinkle 3/4 cup cheese and mushrooms over bottom of shell. Arrange asparagus spears in a spoke fashion over mushrooms or arrange fiddleheads in an even layer. In a medium bowl lightly beat eggs with half and half, lemon peel, juice, salt and pepper, and nutmeg; pour over vegetables. Sprinkle with remaining cheese. Set the pie on a cookie sheet in a preheated 350° oven. Bake for 45 minutes or until knife inserted comes out clean.