In a medium bowl, combine the graham cracker crumbs, granulated sugar, ground cinnamon, and melted unsalted butter. Mix until the texture resembles wet sand. Press the mixture evenly into the bottom of a 9-inch springform pan, ensuring it's tightly packed. Place the pan in the refrigerator to chill for at least 30 minutes.

In a large mixing bowl, beat the cream cheese with an electric mixer on medium speed until smooth and creamy, about 2-3 minutes. Gradually add the granulated sugar and flour, mixing until fully incorporated. Blend in eggnog, ground nutmeg, and vanilla extract, followed by the eggs one at a time, beating just until combined. The filling should be smooth and free of lumps.

Preheat your oven to 325°F (163°C). Carefully pour the cream cheese filling over the chilled crust in the springform pan. Place this pan in a larger baking dish and fill it with hot water to create a water bath. Bake for about 60 minutes, or until the edges are set, and the center slightly jiggles when lightly shaken.

Once baked, turn off the oven and crack the door open. Let the cheesecake cool in the oven for an hour. After that, remove it from the water bath and let it cool to room temperature. Cover it with plastic wrap and refrigerate for at least 6 hours or overnight.

In a chilled mixing bowl, beat the heavy whipping cream on medium-high speed until it starts to thicken. Gradually add the powdered sugar, ground nutmeg, and vanilla extract, beating until soft peaks form.

Once fully chilled, carefully unmold the cheesecake from the springform pan. Top with the nutmeg whipped cream and dust with extra ground nutmeg if desired. Slice into wedges and serve.