In food processor (or use electric mixer with large bowl), blend the cream cheese with the sweeteners and cocoa powder.
Blend in large egg, then blend in egg yolks.
Blend in sour cream, heavy cream, melted chocolate, and vanilla extract. Scrape sides of processor or bowl as needed.
Pour cream cheese mixture on top of crust in pan. Smooth top with rubber spatula.
Place rack in pressure cooker, then add in 1.5 cups of water.
Make a foil sling and place over rack making sure ends are long enough to extend top of pressure cooker.
Place cheesecake pan over sling and cover loosely with foil to prevent condensate dripping on top. Fold tops of sling loosely over cheesecake.
Cover pressure cooker and set to maximum pressure for 20 minutes. When time is up, allow pot to sit for 15 minutes at natural pressure release.
Open lid and use sling to lift cheesecake out and move to cooling rack.
Allow to cool for an hour or so, then refrigerate for a couple hours before removing side of pan.
For best results, the cheesecake should be allowed to sit overnight in the refrigerator.
Serve close to room temperature for a softer texture.