Make the batter: Lightly butter a 7-inch springform pan, coat it with the turbinado sugar, and tightly wrap the outer bottom and sides of the pan with foil to prevent water seepage; set aside. Using an electric mixer set on low speed, beat the cream cheese and 1 cup peanut butter in a medium bowl until combined. Add confectioners' sugar, brown sugar, and cornstarch. Beat in the eggs, one at a time. Add the sour cream and vanilla and beat until incorporated. Add the melted chocolate and mix well.
Prepare the cake: Pour the batter into the prepared pan and spread evenly. Place two sheets of paper toweling across the top of the pan and cover with 1 sheet of foil. Create a foil handle by scrunching a 32-inch-long piece of foil and place it under pan, then bring up each side to create the handle.
Cook the cake: Place the pressure cooker's trivet accessory in the bottom of the pan and add 2 cups water. Using the foil handle, lower the cake pan into the pressure cooker. Seal the pressure cooker lid and bring the cooker to high pressure. Reduce heat just enough to maintain high pressure and cook for 22 minutes. Quick-release the pressure and carefully remove lid. Remove cake pan and place on a wire rack to cool completely. Refrigerate overnight.
Top the cake: Combine the peanuts, chocolate wafers, melted butter, and salt in a small bowl; set aside. Spread the melted 3 tablespoons peanut butter on top of cake and top with peanut and chocolate-wafer mixture.