Grease a 20cm springform cake tin with butter and line the base and sides with greaseproof paper.
To make the base, place the biscuits into a sealed food bag and give them a bash with a rolling pin until they are coarse crumbs.
Pour into a mixing bowl and mix with the melted butter and the salt.
Tip the mixture into the prepared cake tin and push down firmly with your hand to form an even layer.
Chill in the fridge while you prepare the filling.
To make the Drambuie butterscotch sauce, put the butter, sugar and golden syrup in a medium heavy-based pan.
Heat gently until the sugar has dissolved then simmer for another 5 minutes.
Turn off the heat then add the Drambuie and slowly stir in the double cream, until smooth.
Stir in a pinch of salt. Allow too cool.
To make the filling, beat together the soft cheese and icing sugar until smooth and thick, then beat in the double cream until beginning to thicken, being sure not to over-whip the mixture.
Pour half of the Drambuie butterscotch into the soft cheese mixture and fold through.
Set the rest of the butterscotch aside.
Spoon the cheese mixture over the biscuit base, smoothing it in an even layer with a palette knife.
Cover and chill in the fridge for at least two hours, or overnight.
The popcorn is best served fresh so if you are making the cheesecake a day ahead, make the popcorn just before assembling.
Heat the oil and popcorn kernels in a heavy-based pan with the lid clamped on.
Once the kernels begin to pop give the pan a shake to stop them catching and remove from the heat once the popping has slowed right down.
Open the lid slightly to allow the steam to escape, removing it completely once the popping has stopped.
Meanwhile, gently warm the butterscotch until it is pourable again. Pour about 4 tablespoons over the popcorn and mix so that it’s coated in the sauce.
Pile the popcorn on top of the cheesecake and pour some more sauce over the top, drizzling it down the sides of the cheesecake.
Sprinkle with sea salt flakes. Serve the cheesecake with any remaining butterscotch in a jug.