Line the sides of 7-inch springform pan with parchment paper (this will help to keep the sides smooth).
In a small bowl, stir together crushed Oreo cookies and melted butter and press the crumbs into the bottom of the prepared pan with your fingers.
Place the pan with Oreo crust in freezer for 10-15 minutes. This will help solidify the crust.
Coarsely chop 8 Oreo cookies for the cheesecake itself and 5 for the topping. Set them aside separately.
In the large bowl, beat the cream cheese with sour cream, vanilla and sugar until smooth. Add corn starch. Next add eggs, making sure to scrape down the bowl in between each egg. Fold in 8 chopped Oreo cookies.
Pour batter into prepared pan and cover with foil.
Pour 1.5 cups of water into the Instant Pot and place the trivet in the bottom of the pot. Hit Sauté and bring water to a boil.
Place the cheesecake pan on the trivet inside instant pot.
Lock the lid into place and make sure the vent is closed "sealing". Press the "Pressure Cook" (or "Manual" on some models) button and cook on high pressure for 30 minutes.
When the Instant Pot beeps, hit the "Keep Warm/Cancel" button to turn off the pressure cooker. Allow the pressure to release naturally for 10 minutes and then do a quick release to release any pressure remaining in the pot.
Remove the cheesecake from the pot to a cooling rack. Allow it to cool to room temperature for 30 minutes and top with remaining chopped Oreos.
Once the cheesecake has cooled, refrigerate it for at least 6 hours, or preferably overnight.