Prepare the biscuit base:
Preheat the oven to 175°C (350°F). Grease an 18x28cm (7x11-inch) baking pan.
In a medium bowl, combine the crushed Tim Tam biscuits and melted butter.
Mix until well combined and press firmly into the bottom of the prepared baking pan.
Set aside.
Make the cheesecake filling:
In a large bowl, beat the cream cheese and sugar together until light and fluffy.
Add the sour cream, vanilla extract, and eggs one at a time, beating well after each addition.
Pour the cheesecake filling over the prepared biscuit base.
Bake the cheesecake:
Bake for 35-40 minutes, or until the filling is set and the edges are slightly golden brown.
Turn off the oven and leave the cheesecake inside to cool completely.
Make the chocolate ganache:
In a small saucepan, heat the heavy cream over medium heat until it just starts to simmer.
Remove from the heat and add the chocolate chips.
Stir until the chocolate is melted and smooth.
Pour the ganache:
Pour the chocolate ganache over the cooled cheesecake, spreading it evenly to cover the top.
Refrigerate for at least 2 hours, or until the ganache is set.
Cut and serve:
Once set, use a sharp knife to cut the cheesecake into 12 generous slices.
Serve chilled and enjoy!