Reduce the heat to 325F and move on to making the cheesecake filling.
In a large bowl, using an electric mixer or a stand mixer, beat the softened cream cheese and sour cream until it's smooth and creamy.
16 oz cream cheese, ¼ cup sour cream
Add the granulated sugar and continue to beat until well combined.
½ cup granulated sugar
Mix in the eggs one at a time, ensuring each egg is fully incorporated before adding the next.
2 large eggs
Add the eggnog, vanilla extract, ground nutmeg, and flour to the cream cheese mixture. Mix until the batter is smooth and all ingredients are fully combined.
½ cup eggnog, 1 teaspoon vanilla extract, ½ teaspoon ground nutmeg, 2 tablespoon all-purpose flour
Pour the cheesecake mixture over the graham cracker crust in the pan. Smooth the top with a spatula.
Bake in a water bath the preheated oven for about 40-45 minutes, or until the edges are set and the center is slightly jiggly.
Remove the cheesecake bars from the oven and let them cool in the pan on a wire rack. Once they've cooled to room temperature, transfer them to the refrigerator and chill for at least 3-4 hours, or overnight.
Once the bars have chilled and set, use the parchment paper overhang to lift them out of the pan. Cut into squares.
If desired, top each bar with a dollop of whipped cream and a sprinkle of ground nutmeg before serving.
Whipped cream, Ground nutmeg