Preheat the oven to 160°C and grease a 6-inch (15 cm) springform pan.

Make the crust: In a bowl combine the crushed Oreos and melted butter and mix until combined. Pressure the mixture into the bottom of the pan then bake for 10 minutes. Remove from oven and let cool completely before adding the filling.

Make a ganache. Place the chocolate in a microwaveable bowl and heat for 30 second intervals, stirring after each time until all the chocolate has melted, then pour the cream over the chocolate and mix until combined. Set aside.

In a large bowl, beat the cream cheese for 1-2 minutes with a hand mixer until light and fluffy.

In a small bowl mix together the sugar and orange zest. Add the orange zest/sugar mixture, cocoa powder and salt to the cream cheese. Beating by hand until smooth.

Add the sour cream, vanilla extract, orange juice, and eggs and beat by hand until just combined.

Fold the chocolate ganache into the cream cheese mixture until fully incorporated then pour the mixture into the cooled crust.

Bake the cheesecake for 30 minutes then reduce the heat to 120°C and bake an additional 30-35 minutes. Turn off the oven, crack the door, then let the cheesecake sit in the warm oven for another 30 minutes.

Remove the cheesecake from the oven and allow to cool at room temperature for at least 2 hours and then move to the refrigerator for at least 6 hours but preferably overnight before releasing from the pan.