In a medium bowl, mix together graham cracker crumbs, granulated sugar, and ground cinnamon. Pour in melted unsalted butter and stir until it resembles wet sand. Press the mixture into the bottom of a 9-inch springform pan. Chill in the refrigerator while preparing the filling.

In a large bowl, beat softened cream cheese until smooth. Gradually add granulated sugar and flour, mixing until combined. Slowly pour in eggnog, ground nutmeg, and vanilla, mixing until creamy and lump-free.

Add large eggs one at a time, mixing gently after each addition. Ensure the filling is smooth and thick but pourable.

Pour filling into the chilled crust, spreading evenly. Prepare a water bath by placing the springform pan in a larger dish filled with hot water.

Preheat oven to 325°F (163°C) and bake the cheesecake for about 60 minutes, until edges are set and center jiggles slightly. Turn off the oven and leave the door ajar for 1 hour.

Remove the cheesecake from the oven and water bath, cool at room temperature for 1 hour. Cover with plastic wrap and refrigerate for at least 6 hours or overnight.

Before serving, beat cold heavy whipping cream, add powdered sugar, nutmeg, and vanilla, whipping until soft peaks form.

Unlock and remove the sides of the springform pan. Top with whipped cream and additional nutmeg if desired. Slice and serve.