In the bowl of a food processor, add Biscoff cookies and pulse until processed into fine crumbs.
Add brown sugar and salt; process until blended, about 15 seconds.
With the appliance running, slowly pour in melted butter and vanilla extract through the feed tube.
To know if it’s the right consistency - take a measuring spoon, compress the mixture, drop it in your hand and if it holds its shape, then it’s fine – it should be like damp sand.
Pour into a 9-inch non-stick springform pan. Using a small measuring cup or glass, press the crumbs firmly into the bottom and up the sides as high as possible.
Carefully transfer the pan to the preheated oven and bake for 7 minutes.
Remove from the heat and place it on a rack. Set aside to cool while making the filling.
FILLING
In the bowl of a stand mixer, add cream cheese and, using the paddle attachment, process on medium speed until creamy and smooth, about 2 minutes; clean the sides and bottom of the bowl.
While the appliance is running, slowly add sugar, salt, and vanilla. Process until the mixture is well combined and smooth, cleaning the sides and the bottom of the bowl a few times as well as the paddle attachment.
Add the eggs, one at a time, mixing well between each addition and scraping down the bowl.
Add pumpkin purée, brown sugar, sour cream and Pumpkin Pie spice; process until blended, cleaning the sides and the bottom of the bowl.
In a small sieve, add cornstarch and tap the side to sift it into the mixture. Process on low speed at first until mostly blended before increasing back to medium, making sure to clean the sides and bottom of the bowl.
Pour the batter into the prepared cooled crust and transfer to the 350ºF preheated oven; bake for 10 minutes.
Reduce the heat to 300ºF and continue baking for an additional 50 to 60 minutes or until the edges are slightly puffed.
Turn off the oven and leave the cheesecake in with the door closed for 2 hours.
Remove the cheesecake from the oven to a wire rack and let it cool for 30 minutes or until it reaches room temperature. While still warm, run a thin knife around the outside edge to help release the cake from the pan later.
Transfer it to the fridge for at least 8 hours but preferably overnight.
When ready to serve, gently remove the sides and run an angled spatula under the bottom to release the cake from the base; carefully transfer to a cake server. Decorate with whipped cream if desired.