Heat the oven to 400 degrees.
Line a nine-inch pie plate with the pastry. By all means build a rim with the pastry and flute it. This is essential for the amount of custard indicated in this recipe.
Cover the bottom of the pastry with a round of parchment paper and add enough dried beans or peas to partly fill the shell. Bake 10 minutes.
Reduce the oven heat to 375 degrees. Remove and discard the beans and parchment paper and set the pastry-lined pie plate aside.
Cook the mushrooms in a little olive oil or butter until browned and remove from skillet. Cook the onion and asparagus in the remaining fat until the onion is transparent and asparagus is bright green.
Combine the eggs, cream, salt, and pepper. Sprinkle the mushrooms, asparagus, onion and cheeses over the inside of the partly baked pastry.
Strain the cream mixture over the vegetable-cheese mixture. Slide the pie onto a baking sheet.
Bake the pie until a knife inserted one inch from the pastry edge comes out clean, about 50 minutes. Remove to a wire rack. Let stand 5 or 10 minutes before serving.
Of course, you can start with a store-bought frozen crust or ready-to-roll pie dough. What you can’t skip is blind-baking the rolled dough: Set a sheet of parchment paper over your dough-lined pie dish, fill it with dried beans and bake. Mr. Claiborne lets it go for 10 minutes to set the sides; I double that time so that even the bottom is completely dry because I really hate even the slightest uncooked bottom crust. If the pastry cracks with my long blind bake, I brush some egg white in the crevices to seal them. While the crust bakes, you can prep the fillings. The cheeses, vegetable mixture and custard can be used right away or refrigerated in separate containers, and that blind-baked crust will keep at room temperature for a few days. An hour or so before you want to serve your warm quiche, fill the crust and slide it in the oven. Easy!
