Pre heat the oven to 275F. Stir the milk, cream, sugar and vanilla in a heavy large saucepan over med. heat until sugar dissolves and milk mixture is warm but not boiling (apx. 10 min.)
Remove from heat and allow to cool slightly. Whisk the whole eggs and the egg yolks together in a large bowl, gradually whisk into the warm milk misture. Place the croissant peices in a 13x9 inch baking dish.
Pour the custart (milk & egg mixture) over the croissant pieces (if you strain the mixture as your pour it over, you will have a smoother, creamier custard) and sprinkle the raisins over. Press gently to submerge the croissants and raisins. Let stand for 20 min. to allow the croissants to absorb some of the custard. Place the baking dish in a large roasting pan. Set the roasting pan on the oven shelf. Add enough warm water to the roasting pan to come half way up the sides of the baking dish.
Bake until the pudding is firm to the touch, about 2 hrs. Serve warm.