Grease and line a 22cm (8 ¾ inch) diameter pie tin. Put the crushed biscuits in a bowl and mix in the melted butter. Spoon into the prepared tin and press down well using the back of a spoon to cover the base and sides. Chill until required.
Meanwhile, make the filling. Pour 250ml (9fl.oz) cold water into a bowl and stir in the Vege-Gel powder. Set aside.
Put the sugar and golden syrup in a saucepan with 60ml (4 tbsp) water. Stir over a low heat until melted. Bring to the boil and cook for about 5 minutes until richly golden and caramelised.
Immediately remove from the heat and stir in the butter and cream, taking care as the mixture will hiss and bubble, until well blended.
Pour in the Vege-Gel mixture and mix well. Return to the heat, stirring until the mixture begins to boil.
Working quickly, pour the hot caramel jelly mixture into the biscuit base and leave to cool completely. Chill for 2 hours before serving.
To serve, carefully loosen the pie from the tin, allowing the crumbly top edge of the biscuit crust to fall round the edge of the set jelly filling. Slide the pie from the tin on to a serving plate. Sprinkle with a few flakes of salt and serve immediately with pouring cream.