Preheat the oven to 350 degrees F. Spray a 9x13 inch pan with nonstick spray.
In a bowl, stir together the crushed pretzels, sugar and cocoa powder. Add in the melted butter and mix until fully combined. Press the crust into the prepared pan.
Bake the crust for 10 minutes.
While the crust is baking, make the filling. In the bowl of your electric mixer, beat the cream cheese until creamy and smooth.
Add in the sugar and beat until combined. Add the eggs one at a time, beating until each is just incorporated. Add in the pumpkin, sour cream and vanilla extract until just combined, being sure to scrape the bottom of the bowl. Beat in the salt and pumpkin pie spice. Do not over beat!
Pour the filling on top of the baked crust. Bake for 50 to 60 minutes, or until the center is no longer fully jiggly - a little bit of movement is okay.
Remove the pan and let it cool completely. Cover it and place in the fridge for at least 6 hours or even overnight.
Slice the bars into squares. Top with fresh whipped cream and a sprinkle of cinnamon or pumpkin pie spice!