Line a 9-inch springform pan with greaseproof paper at the base and sides. Place shortbread cookies in a plastic bag and crush them into fine crumbs using a rolling pin. Transfer the crumbs to a mixing bowl and stir in the melted butter until fully combined. Press the mixture firmly into the prepared tin and refrigerate for about 1 hour to set.

If using the caramel layer, spread the caramel sauce evenly over the chilled shortbread base and return it to the refrigerator while preparing the cheesecake filling.

In a large mixing bowl, beat the full-fat cream cheese with an electric mixer until softened. Add the sieved powdered sugar and mix until smooth. Pour in the heavy cream and caramel sauce, then whip the mixture until thick and creamy.

Retrieve the prepared base from the fridge and evenly spread the cheesecake filling over it. Smooth the top with a spatula, then refrigerate for at least 3 hours to firm.

Finely chop the chocolate and place in a heatproof bowl. In a small saucepan, heat the heavy cream over medium-high heat, stirring constantly, until hot but not boiling. Pour the hot cream over the chopped chocolate and allow to sit undisturbed for 3-4 minutes. Stir gently until the ganache becomes smooth and glossy, then let it cool to room temperature for about 15 minutes.

Once cooled, pour the ganache over the set cheesecake layer and spread evenly. Return the cheesecake to the refrigerator and allow it to set for a minimum of 4 hours, preferably overnight.

For decoration, drizzle with melted white chocolate if desired.