Preheat oven to 325°F. You are going to partially bake your pie crust. Place your 9-inch pie pan on a cookie sheet (which makes transporting in and out of the oven easier). Prepare your pie crust by placing it in your pie pan. Crimp the pie edges, and prick the bottom and sides with a fork. Place foil inside the pie crust and add pie weights or dried beans. Bake for 12 minutes. Remove from oven and set aside. Remove the foil and pie weights.
Reduce the oven to 300°F.
While the pie crust is prebaking, in a 3-quart saucepan, place the flour, sugar, brown sugar, nutmeg and salt. Use a whisk to stir together to remove any clumps and to mix.
Next, add the heavy cream, milk and vanilla extract. Place the pan over medium heat and whisking frequently, cook until thick and creamy (about 13 to 15 minutes). It should not come to a boil. You need to whisk or stir frequently to keep the milk from burning.
Pour into a partially baked, yet still hot, pie shell.
Bake for 60 minutes (if using a glass dish, 50 minutes if using metal). It will be a little jiggly in the middle still when time is up, but most of the pie will not jiggle. Remove from oven and let it cool. As it cools, it will begin to firm up. Let the pie cool for about an hour, and then you can place it in the fridge to continue to firm up.
Optional cool whip dollop when served.