Preheat your oven to 300° F.
Bring the raisins to a boil in water and then drain. Set aside.
Split the vanilla bean, scrape out the seeds and place the pod and the seeds in a saucepan with the milk and sugar. (If you're using vanilla extract add it at the very end).
Bring the milk mixture to a boil.
Meanwhile, whisk the eggs and egg yolks.
When the milk has boiled remove the vanilla pod. SLOWLY pour the milk mixture into the eggs, in a thin stream, whisking CONSTANTLY. You can even pour it intermittently. If you pour it in too fast you will scramble the eggs. Strain it into a bowl and skim any foam off the surface. If you'd like, you can add some of your favorite liqueur to the custard now.
Toss the bread cubes with the melted butter and then scatter them and the raisins in a 1½ - 2 quart baking dish.
Pour the custard over the bread. Now place the baking dish into a larger pan, such as a roasting pan. Pour hot tap water in the larger pan until it comes at least halfway up the baking dish. Bake for 45 minutes to an hour or until the custard sets.