Place the raisins in a small bowl. Pour over the rum and set aside (at room temperature) for several hours or overnight. Drain the raisins and reserve the rum.

Preheat the oven to 150C. Grease an ovenproof dish - square or round - measuring at least 5cm deep and about 25cm across.

Place a layer of croissant pieces in the base, sprinkle with raisins, add another layer of croissants, then raisins and so on. Reserve a handful of raisins to sprinkle on top.

Bring the milk, cream, salt, vanilla bean and reserved rum to the boil in a saucepan. Remove from heat and discard the vanilla bean. Set aside.

In a large bowl, whisk the eggs and sugar together then slowly pour in the milk mixture, whisking constantly.

Carefully pour the custard over the croissants, sprinkle with reserved raisins and bake for an hour, or until the custard is just set.

Serve with cream or ice-cream.