Place the cream, milk, vanilla extract and orange zest into a saucepan and bring to a simmer.
Place the egg, egg yolks and sugar into a large bowl and whisk together.
Gradually pour the cream mixture onto the eggs, whisking continuously to make a smooth custard.
Lightly grease a microwave-proof dish and place the croissant slices in the base of the dish. Sprinkle over the sultanas and pour over the custard mixture.
Place in the microwave and cook on full power for four minutes, or until set.
To serve, dust the pudding with icing sugar and caramelise with a mini-blowtorch. Place servings of the pudding into two bowls.