Blitz all the Oreos for the base and filling (total 420g / 14.8 oz) into a fine crumb in the food processor. That saves you doing the job twice.
Make the Oreo base
Put 250g (8.8 oz) of Oreo crumbs into a bowl.
Add the melted butter and stir until combined.
Tip the crumb into a greased 23cm (9in) springform tin. Press down firmly to create an even base, then place in the fridge to chill.
Make the chocolate Oreo cheesecake filling
Put the cream in a large bowl and whip until very thick.
Add the cream cheese (light and full fat) and sugar. Whisk until thick and stiff.
Add the cooled chocolate. Whisk to combine. It should now be getting very thick - almost like mousse.
Add the hot chocolate powder and the remaining 170g (6 oz) Oreo crumbs. Fold together. Once combined, your mixture should be very thick and stiff.
Retrieve your tin from the fridge and tip the filling on top of the base. Level off with a spatula, cover and return the tin to the fridge to chill overnight.
To serve
When you're ready to serve, run a warm knife around the edge of the tin then release the springform lock.
Serve slices to plates and top with chocolate sauce.
Finish by pushing an Oreo, standing up into the top of each slice.
Video
Notes
Chocolate Oreo cheesecake needs to be kept in the fridge. It contains a lot of fresh dairy so needs to be chilled, other than when serving.Keep your cheesecake covered in the tin until you're ready to serve. Any leftovers can be transferred into a suitable airtight container and put back in the fridge.Assuming you've used freshly opened cream and cream cheese, this cheesecake will keep in the fridge for up to five days. Make sure to double-check the Use By dates on the cream and cream cheese too - if they are due to go off in less than 5 days, then so is your cheesecake.