Use a food processor to blitz the shortbread biscuits to a fine crumb. If you don't have a food processor put the biscuits into a ziplock bag and bash them up with a rolling pin.
Melt the butter in the microwave - this usually takes about 45 seconds. Pour the melted butter into the biscuit crumbs and mix well.
Transfer the biscuits into a baking tin and press them down using your hands, or a spoon. Put the baking tin into the fridge while you make the caramel.
Put the butter, sugar, golden syrup and condensed milk into a medium saucepan over a high heat. Stir continuously using a wooden spoon or rubber spatula. Let the caramel boil for 5-7 minutes, it's ready when it's a deep golden colour and has a fudge-like consistency. When it's ready take the pan off the heat and leave the caramel to cool for 20 minutes.
Pour the cooled caramel over the biscuit base and put the baking tin back in the fridge while you make the filling.
Put the cream cheese and caster sugar into a large mixing bowl and beat together using an electric handheld whisk. Add the lemon juice, vanilla extract and Carnation caramel and beat again.
In a separate bowl, whisk the double cream until it forms stiff peaks. Transfer the whipped cream into the cream cheese mixture and fold the mixture together.
Check the caramel layer has cooled and is set. Spoon the cheesecake filling on top of the caramel layer and smooth with the back of a spoon. Cover with clingfilm and chill for at least 12 hours.
Chop the chocolate into small pieces and put them into a heatproof bowl. Pour the double cream into a small saucepan and place it over a medium heat. Remove from the heat just before it reaches boiling point. Pour the hot cream over the chopped chocolate and leave it to sit for a few minutes.
Next, vigorously mix the cream and chocolate mixture using a rubber spatula or wooden spoon. The ganache will look thick and glossy. Pour it on top of the cheesecake filling and then put the baking tin back into the fridge for about an hour to set.
When the ganache has set you can remove the cheesecake from the baking tin. Whip the double cream to soft peaks and put it into a piping bag fitted with an open star nozzle. Pipe swirls of cream on top of the cheesecake and decorate each swirl with a square of Millionaire's shortbread. Add some gold sprinkles for a final flourish.