Preheat oven to 350 degrees. Line a 9 x 9 inch baking pan with heavy-duty foil or parchament paper (so that there is an overhang on at least 2 sides) and spray lightly with nonstick cooking spray.
In a medium bowl, combine the graham cracker crumbs, melted butter, sugar, and salt. Stir until well combined. Pour the crumb mixture into the prepared baking dish.
Use your hands or a spatula to press the crumbs in the bottom of the baking dish. Bake for 10 minutes.
In a large bowl, beat the cream cheese with a mixer on medium speed until fluffy, about 2 minutes. Add the granulated sugar and beat for an additional couple of minutes, until smooth.
Add the eggs and yolk, eggnog and vanilla and beat again until completely combined and smooth.
Now it's time to add bourbon if you like, or leave as it is, it would be great eather way. Finally, beat in the flour, nutmeg and salt and mix until smooth.
Pour the eggnog cheesecake filling over the graham cracker crust. If using a water bath, place the baking pan in a larger pan, and add enough hot water to come halfway up the sides of the baking pan.
Bake until just set, 40 to 45 minutes. Remove the baking pan from the water bath, and transfer to a wire rack. Let cool for 30 minutes, then refrigerate for at least 3 hours or overnight.
* - You will know the cheesecake is done when it appears almost set in the middle.
* - If baking the bars without bath, bake for about 30-40 minutes.
Remove from oven and let cool on a baking rack for one hour. Refrigerate for at least 3 hours or overnight.
Remove from the pan using the foil, and cut into 16 bars and sprinkle with nutmeg or sprinkle with graham crumbs and/or crystallized ginger, or leave as it is.