This is the quiche that I make most often. I created this recipe because I just love a good quiche. I use canned mushrooms for convenience, but you may use fresh sautéed mushrooms, if desired. Sprinkle with a little black truffle salt, if available, for even more deliciousness!
Gather and prep all ingredients (thaw pie crust, if using frozen.)
Place pie/pastry crust on rimmed baking sheet. Place oven rack in lowest position in oven; preheat oven to 375ºF.
Pour cream and milk into a microwave-safe bowl or 2 cup glass measuring cup; warm in microwave 3 minutes at 1/2 power or 45 seconds at full power, stir and warm an additional 45 seconds at full power (do not overheat.) If this step is skipped, it will increase baking time to approximately 1 hour.
Break 3 eggs into mixing bowl.
Break the fourth egg; separate white from yolk over a small bowl; put yolk in mixing bowl with the eggs, set mixing bowl aside.
Using a fork, beat the egg white in small bowl until slightly foamy.
Using a pastry brush, brush uncooked crust with egg white; add any remaining egg white to eggs in mixing bowl.
Use a whisk to beat together well, eggs, remainder of beaten egg white, grating of nutmeg, salt and pepper.
Add warm cream/milk; whisk well.
Add mushrooms, chives and onion/shallot; stir well.
Evenly scatter cheese over bottom of pie crust.
Pour egg mixture into crust.
Bake (on baking sheet) for 45 to 50 minutes at 375ºF. Top of quiche should be lightly browned and inflated (it will fall slightly as it cools.)
Allow to cool for 20 to 30 minutes before slicing.