Fill a pie with apples sliced thin, using enough to make the pie at least an inch thick when done. Add a little water to the apples, and cover with a top crust which is a little richer than the under one. This is done by rolling out a part of the same paste, covering it with bits of butter, folding it together, and rolling it again, repeating the operation two or three times. Cut a few slits in the paste to let out the steam while cooking. Brush the top with beaten yolk of egg.
When the pie is baked, and while it is still hot, lift off carefully the top crust; add sugar, nutmeg, and a little butter, and mix them well with the apples. Replace the top crust, and dust it with powdered sugar. Apple pies seasoned in this way are better than when seasoned before being baked.