Preheat the oven to 350°F (175°C). In a mixing bowl, combine chopped walnuts, graham cracker crumbs, sugar, and melted butter. Mix until well combined.

Press the mixture firmly into the bottom of a 9x13 inch baking pan to form an even layer. Bake for 10 minutes, then remove from the oven and let cool.

In a large mixing bowl, beat the softened cream cheese until smooth using an electric mixer.

Add pumpkin puree, sugar, eggs, vanilla, cinnamon, nutmeg, ginger, and salt. Mix until fully combined and smooth.

Pour the pumpkin cheesecake filling over the cooled walnut crust and spread evenly.

In a separate bowl, combine flour, brown sugar, and cold butter. Use a fork or pastry cutter to mix until crumbly. Stir in chopped walnuts.

Sprinkle the streusel topping evenly over the cheesecake filling.

Bake in the preheated oven for 45-50 minutes, or until the center is set. Remove from oven and let cool completely.

Once cooled, cut into bars and serve. Store leftovers in the refrigerator.