Make and Bake the Pastry:

1. Add both the flours, brown sugar, salt and spices to the bowl of a food processor. Pulse until combined. Add in butter and pulse 5 times.
2. Whisk together one egg and molasses in a small bowl. With the motor running, pour the molasses mixture into the flour and let process until the dough forms together into a cohesive ball.
3. Remove the dough from the processor and form into a disk. If desired, cut off about 2 ounces of dough to use for cookies (see note for more info about baking cookies). Wrap in plastic wrap and let chill until semi-firm, about 1 hour.
4. On a lightly floured surface, roll out the pie dough to an 11″ circle and line a 9” pie plate with the dough, crimping the edges as desired. Place in the freezer to firm up for 10-20 minutes.
5. Preheat oven to 375ºF and place one oven rack in the second to lowest spot and one in the middle.
6. Line the pie dough with a parchment round piece of paper and then add pie weights to fill (such as dry rice, bean or lentils), making sure to push the pie weights to the edges. Bake for 20 minutes on the lower rack, then remove from the oven and remove the parchment and pie weights. Return to the oven and bake for an additional 5-10 minutes until the pastry is fully baked through.
7. While the crust is still hot, crack one egg and separate the yolk from the white. Set the yolk aside for another use. Whisk the egg white to break it apart and brush a thin layer of the egg white with a pastry brush all over the hot pie crust. The heat from the crust should cook the egg white. If your pie has cooled down too quickly, you can place it back in the oven for a few minutes until the egg white is set. It should no longer look wet. Set aside the prepared crust until ready to use.
8. Lower the heat to 325ºF

Make and Bake the Custard:

1. Add sugar, nutmeg, salt and eggs in a medium bowl and whisk together. Add in the eggnog, vanilla extract and bourbon (if using) and whisk to combine. Strain the mixture through a fine-mesh strainer twice.
2. Pour into the baked pie pastry. Cover the edges of the pie crust with tin foil or a pie shield to prevent the edges of the crust from getting too dark.
3. Place the pie onto your oven’s middle rack and bake it for 50-60 minutes, or until the custard has puffed about 2-3” from the edge but still slightly wobbly in the middle. The pie should have a temperature of about 180ºF.
4. Remove the pie from the oven, and place it on a rack to cool. When it’s completely cool, refrigerate for at least 6 hours. When ready to serve, decorate with cookies, if desired. Serve optionally with whipped cream and/or a fresh grating of nutmeg.