Pour the whiskey over the sultanas and leave them to soak for at least 1-2 hours but preferably overnight.
Put the milk and cream in a pot with add the vanilla extract and bring to just under a boil.
In a large bowl, beat the eggs and sugar until they are thick and pale in colour. Pour the hot milk and cream over the egg mixture whisking all the time. Sieve the mixture back into the pot and simmer gently for about 20 minutes until the mixture coats the back of a wooden spoon.
Butter an oven dish and place one third of the sliced brioche on the bottom. Sprinkle with half the whisky soaked raisins and then place some more brioche slices on top and sprinkle with the rest of the sultanas and put a final layer of brioche on top.
Pour the milk and cream mixture evenly over the pudding - do this gradually so that all the mixture is absorbed by the brioche. Put the pudding in a pre-heated oven at 180°C for about 25 to 30 minutes, until it has risen.
To serve, sprinkle some brown sugar on the pudding and use a blowtorch to caramelise it, serve warm with some ice cream.