Divide the raspberries between 4 ramekins, then scatter over the sugar and press down slightly with the back of a spoon. Whip the cream until it holds its shape, then fold the custard and basil through the cream. Spoon the creamy mixture over the raspberries and smooth over the tops. Leave the ramekins in the freezer for about 30 mins to just set the cream - you don't want it set solid. The creams can now be frozen for up to 2 weeks, but should be defrosted slightly in the fridge for a few hours before serving.
To serve, dust each ramekin evenly with a layer of icing sugar, then use a blowtorch to caramelise the top. Leave the caramel to harden for 1 min, then serve straight away.