Prepare the crust:

• Preheat the oven to 160°C (320°F). Grease a 9-inch springform pan.
• Combine the crushed chocolate biscuits with melted butter. Press the mixture into the bottom of the pan to form an even crust. Bake for 10 minutes, then let it cool.

Make the cheesecake layer:

• Beat the cream cheese and sugar together until smooth. Add the eggs one at a time, beating well after each addition.
• Stir in the vanilla extract and the melted dark chocolate until fully combined.
• Pour the mixture over the cooled crust. Bake for 45-50 minutes or until the centre is set. Allow the cheesecake to cool completely.

Prepare the mousse layers:

• For each mousse (dark, milk, and white chocolate), melt the chocolate over a double boiler or in the microwave. Set aside to cool slightly.
• In separate bowls, whip the heavy cream until soft peaks form.
• Fold the whipped cream into the melted chocolate for each mousse, one layer at a time.

Assemble the cheesecake:

• Once the cheesecake has cooled, spread the dark chocolate mousse over the cheesecake layer. Refrigerate for 15 minutes to set.
• Follow with the milk chocolate mousse layer, spreading evenly. Refrigerate again for 15 minutes.
• Finally, spread the white chocolate mousse on top. Refrigerate the entire cake for at least 4 hours or overnight to set completely.

Garnish and serve:

• Decorate the top with chocolate shavings or a dusting of cocoa powder, if desired. Slice and enjoy this rich, decadent Triple Chocolate Mousse Cheesecake!