Step 1: Prepare the Graham Cracker Crust

1. Preheat the Oven: Preheat your oven to 325°F (163°C). Grease a 9-inch springform pan with butter or non-stick spray, and line the bottom with parchment paper for easier removal.
2. Make the Crust: In a medium bowl, combine the graham cracker crumbs, granulated sugar, and melted butter. Stir until the mixture resembles wet sand.
3. Press the Crust: Firmly press the crust mixture into the bottom of the prepared springform pan, creating an even layer. Use the bottom of a measuring cup or glass to help press it down smoothly.
4. Bake the Crust: Bake for 10 minutes, then remove from the oven and let it cool while you prepare the filling.

Step 2: Prepare the Cheesecake Filling

1. Beat the Cream Cheese and Sugar: In a large mixing bowl, beat the softened cream cheese and granulated sugar on medium speed until smooth and creamy, about 2-3 minutes.
2. Add Mascarpone and Sour Cream: Add the mascarpone cheese and sour cream to the cream cheese mixture, beating until just combined. This step ensures the filling is light and velvety.
3. Incorporate the Eggs: Add the eggs one at a time, mixing well after each addition. Be careful not to overmix, as this can create air bubbles that lead to cracks.
4. Add Flavorings: Pour in the eggnog, vanilla extract, nutmeg, and cinnamon. Beat on low speed until everything is evenly mixed. The eggnog and spices bring that classic holiday flavor to the filling.

Step 3: Bake the Cheesecake

1. Pour the Filling: Pour the cheesecake filling over the cooled graham cracker crust, spreading it into an even layer.
2. Water Bath Method: Wrap the outside of the springform pan with aluminum foil to prevent water from leaking in. Place the pan inside a larger baking dish and add enough hot water to reach halfway up the sides of the springform pan.
3. Bake the Cheesecake: Bake for 60-70 minutes, or until the edges are set and the center is slightly jiggly. Avoid opening the oven door frequently to maintain a stable temperature.
4. Cool the Cheesecake Gradually: Turn off the oven, crack the door slightly, and allow the cheesecake to cool for 1 hour inside the oven. This gradual cooling helps prevent cracks.

Step 4: Chill the Cheesecake

1. Refrigerate: Once the cheesecake has cooled to room temperature, cover it with plastic wrap and refrigerate for at least 4 hours, or preferably overnight. This allows the cheesecake to firm up fully.

Step 5: Prepare the Whipped Cream Topping

1. Whip the Cream: In a chilled bowl, beat the heavy whipping cream, powdered sugar, and vanilla extract on high speed until stiff peaks form. Be careful not to over-whip, as it can turn into butter.
2. Pipe or Dollop the Whipped Cream: Transfer the whipped cream to a piping bag fitted with a star tip, or simply dollop it onto the cheesecake for a more rustic look.
3. Decorate: Dust the top of the cheesecake with a sprinkle of cinnamon. Top with chocolate holiday decorations or edible Christmas-themed toppers if desired.

Step 6: Serve

1. Slice and Serve: Carefully remove the cheesecake from the springform pan and place it on a serving plate. Slice into portions and enjoy your festive Eggnog Mascarpone Cheesecake with family and friends.