Preheat the oven to 200C/400F/Gas 6.
For the custard, place the milk, cream, vanilla seeds and pods into a saucepan and bring to a scalding point, then take off the heat.
In a bowl mix the egg yolks and sugar together. Gradually add the vanilla cream mixture, whisking continuously.
For the pudding, spread the ready-made brioche with the butter on both sides.
Grease an ovenproof dish with butter and pour over the custard mixture. Place into the oven to bake for 12 minutes, or until the custard has set.
To serve, sprinkle the pudding with icing sugar.