Grease a baking dish. Mix the chocolate wafer crumbs and cinnamon together. Sprinkle on the bottom of the baking dish – pressing gently.
In a saucepan, melt the chocolate and butter together and set aside.
Process cream cheese in a food processor or electric mixer until very smooth. Add the melted chocolate mixture and process until well-mixed.
Add the whipping cream, vanilla extract, sugar, and eggs, then cocoa powder until all ingredients are well incorporated.
Pour the mixture over crumbs in the baking dish. Cover the baking dish with aluminum foil.
Add water to the bottom of the pressure cooker. Place the baking dish on a trivet in the pressure cooker. Close the lid, bring up to HIGH pressure, then lower heat and pressure cook for 50 minutes.
Remove cooker from heat, let pressure drop naturally. Carefully open the lid, remove the cheesecake from the cooker, and let it cool to room temperature.
Remove the cheesecake from dish, and refrigerate for 8 hours before serving.