Place a piece of aluminium foil on your counter top and place a kitchen towel square in the centre. Position your cheesecake tin over the kitchen towel and tightly wrap the foil around the base.
Spray the tin with cake release and line the bottom and sides with greaseproof paper.
Grind the Oreos to a powder using a food processor. Mix with the melted butter.
Press the crust over the bottom of the prepared pan in an even layer and put in the freezer.
Put the cream cheese and sugar in a bowl and briefly mix together with a hand mixer on low speed until it is smooth and creamy.
Add the peanut butter and caramel and mix again until smooth.
Add the sour cream and vanilla and mix once more.
Add the eggs and mix until combined – do not over mix at this stage!
Pour the filling over chilled crust and gently tap the pan on counter so that it settles.
Cover the top of the pan with a piece of foil.
Pour 350ml (1 1/2 cups) water into your pressure cooker and place the trivet in the bottom of the pot. If your trivet doesn’t have handles, create a foil ‘sling’ by folding a long piece of foil in half lengthwise and place your cheesecake over it to lower (and lift) out of the pot. Tuck the foil sling edges down the side of the pan.
Set vent to ‘sealing’, choose ‘manual’ and set cooking time for 50 minutes at high pressure.
Allow pressure to release naturally for 10 minutes and then manually release.
Lift the pan out of the pressure cooker and carefully remove the foil. The cheesecake should have a bit of jiggle in the centre, but if it seems really jiggly then cover and return to the cooker for a further 5 minutes high pressure cooking (+ 10 mins NPR then manual release).
Remove the foil from the bottom of the pan and place on a cooling rack for a couple or hours.
Place in the fridge for 8 hours or overnight. To remove the cheesecake from the pan run a small knife around the edge to loosen the paper. Place the pan over a tin and gently push the tin downwards to release the middle. Peel the paper off the sides and gently remove the bottom of the cake pan. Transfer the cheesecake to a platter or cake stand.
Make the ganache: place the chocolate and cream in a bowl and microwave for 30 second bursts, stirring after each, until completely melted and smooth.
Spoon (or use a piping bag) the ganache over the perimeter of the cheesecake, encouraging it to drizzle down the sides. Spread the remaining chocolate over the cheesecake to cover.
Whisk the cream, icing sugar and caramel together until it forms peaks. Transfer to a piping bag fitted with a large star tip and pipe over the cheesecake.
Add chocolate sprinkles and a dusting of cocoa powder and serve.