Preheat the oven to 200C/400F/Gas 6.
Grease a small ovenproof dish.
For the custard, place the milk and cream into a heavy-bottomed saucepan and bring to the simmer.
Place the egg yolks and sugar into a bowl and whisk until pale and smooth.
Pour the milk and cream mixture over the sugar and egg yolk mixture and whisk until smooth.
Add the vanilla essence.
For the pudding, spread the butter onto the Madeira cake slices on both sides.
Place the Madeira slices into the greased ovenproof dish and sprinkle over the raisins.
Pour over the custard mixture, and transfer into the oven to cook for 15 minutes.
To serve, remove from the oven and dust with icing sugar.