Add graham crackers to a food processor and process for 20 seconds or until fine crumbs form. Add butter and sugar if using and process for 5 seconds until mixed well.

Pour crust into a 6" springform pan and use a tart shaper or back of spoon to flatten. Set aside.

Rinse the food processor bowl and blade. Add cream cheese and sugar and process until smooth, about 10 seconds. You may have to scrape down the side of the bowl once. Add eggs and process for 10 seconds or until mixed well. Add whipping cream, vanilla, pumpkin and pumpkin pie spice. Process 10 seconds or until mixed well. Pour into prepared crust. Cover the pan with a paper towel and loosely cover with foil.

Place water into the bottom of an Instant Pot.

Place the cheesecake onto the trivet and use the handles to place the cheesecake into the instant pot. Close the lid and the quick pressure release valve. Set the instant pot to manual for 30 minutes and let pressure release naturally for 15 minutes after cooking. Open pot and remove cheesecake, making sure you use hot pads.

Remove the paper towel and foil and let cheesecake set until room temperature. Chill at least 4 hours before serving with whipped topping.