Preheat your oven to 350°F (175°C). In a medium bowl, combine graham cracker crumbs, granulated sugar, and melted butter, mixing until crumbly. Pour mixture into a greased baking pan and press it firmly into an even layer. Bake for about 10 minutes until golden and fragrant, then remove to cool.

In a large mixing bowl, whisk together pumpkin puree, heavy cream, large eggs, sugar, vanilla extract, and pumpkin pie spice until smooth and creamy. Pour the pumpkin mixture over the cooled crust, spreading evenly.

In another bowl, beat softened cream cheese, egg yolk, granulated sugar, and additional vanilla extract until fluffy and smooth. Drop spoonfuls over the pumpkin layer and swirl gently with a knife to create a marbled effect.

Place the baking pan in the oven. Bake for approximately 35-40 minutes until the edges are set but the center has a slight jiggle. Remove from oven and let cool at room temperature.

Cover with plastic wrap and refrigerate for at least 2 hours to set. Once chilled, slice into squares and serve.