Grease the inside of a 20cm loose-bottom deep cheesecake tin and line the base with baking parchment / greaseproof paper.
Blitz the pecan nuts and chocolate biscuits together in a food processor until they resemble course breadcrumbs.
Stir the melted butter into the biscuit mixture, then empty the mixture into the cheesecake tin and press this mixture into the tin to make an even layer.
Chill in the fridge for at least 20 minutes whilst you prepare the cheesecake filling.
To make the cheesecake filling:-
Place the cream cheese, cream, cocoa powder and eggs in a bowl, or into a stand mixer and blend everything together well until smooth.
Pour the mixture over the hardened biscuit base and bake in the oven for approximately 25 – 30 minutes until the top is firm and golden brown.
Remove from the oven and allow to cool on a wire rack for at least 1 hour.
To make the chocolate ganache:-
Pour the cream into a saucepan and gently heat the cream until steam is coming off the top. Do not allow the cream to boil.
Once steam is coming off the top, remove the saucepan from the heat and stir in the broken up chocolate until it has melted completely.
Allow the ganache to cool a little, then pour the ganache over the top of the cooled cheesecake base and put aside for 30 minutes to allow the ganache to cool and set a little. Then move to a fridge for 2 hours minimum.
When ready to serve, carefully remove the cheesecake from the tin and decorate with the pecan nuts.