Crush the digestive biscuits then mix well with the melted butter.
Transfer biscuit mix to the cake pan and press down into the base and up the sides then store in the fridge.
In a bowl, combine the cream cheese, brown sugar, eggs, and cocoa powder When smooth, fold in the melted dark chocolate.
Take cake pan out of fridge and pour the chocolate cream cheese filling on top. Cover the cake pan with foil.
Add 250ml water into inner pot, then place the covered cake pan inside on top of the trivet and secure the lid.
Select Pressure Cook and set the time for 40 minutes and press start.
When the cooking program has finished, allow the pressure to release naturally for 10 minutes then quick release any remaining pressure.
Remove the cheesecake from the inner pot and leave to cool completely.
When ready to serve, top with raspberries and a dusting of icing sugar.