To make the base process the biscuits until they form a crumb then add the cocoa powder, maple syrup and melted butter and stir until thoroughly mixed.
Press into the bottom of a 23 cm/9'' pie dish and place in the freezer for 30 minutes. After 20 minutes start making the filling.
Mash the avocado. To the food processor add the ricotta, cream cheese, lime juice and zest, sugar and avocado. Blend until the ingredients are thoroughly incorporated and the mixture is smooth (do not overblend). Transfer the mixture into a large bowl.
In a separate bowl beat the double cream until soft peaks form (you can do this using either an electric mixer or whisk). Do not overbeat.
Gently fold the whipped cream into the cheesecake filling mixture until thoroughly incorporated.
Remove the cheesecake base from the freezer and spoon the filling mixture over the top. Decorate with lime zest and crushed pistachios (optional). Refrigerate for at least 8 hours (overnight) or freeze for 1 hour then serve.
Use ripe and soft avocado. If using the Hass variety you will need about 1 medium size avocado (however, I recommend weighing the flesh).
Zest the limes first then juice the limes.
Try not to overbeat the cream - it should be thick but soft enough to easily fold into the filling mixture.
Refrigerate this avocado cheesecake for at least 8 hours (overnight) before serving. If you want to serve it sooner freeze it for one hour then enjoy.
Keep refrigerated, covered and consume within 2 days.