2) Slice the croissants in half horizontally. In a 25 x 37.5 x 6.25cm oval baking dish, distribute the bottoms of the sliced croissants, then add the sultanas, then the tops of the croissants (brown side up), being sure the raisins are between the layers of croissants or they will burn while baking.
3) Pour the custard over the croissants and allow to soak for 10 minutes, pressing down gently. Place the dish in a larger one filled with 2.5cm of hot water and cover with aluminium foil, tenting the foil so it doesn't touch the pudding. Cut a few holes in the foil to allow steam to escape.
4) Bake for 45 minutes. Uncover and bake for 40 to 45 more minutes or until the pudding puffs up and the custard is set. Remove from the oven and cool slightly. Serve warm or at room temperature.