Place the dried bread cubes in a bowl and pour the milk over it; let stand for 1 hr.
Preheat oven to 325° F.
Grease a 9" x 13" x 2" baking dish with 1-2 T. butter.
In another bowl, beat together 3 eggs, the sugar, and vanilla extract.
Gently stir egg mixture into bread cubes.
Gently stir in raisins.
Pour into the prepared baking dish.
Place baking dish on the middle rack of the oven, and bake until browned and set, about 1 hr 10 mins.
Cool to room temperature.
Stir 8 T. butter and confectioners' sugar in the top of a double boiler over simmering water until sugar is dissolved and mixture is very hot.
Remove the double boiler from heat.
Beat the remaining egg well and whisk it into the sugar-butter mixture.
Remove sauce pan from double boiler base and continue beating until sauce has ooled to room temperature.
Add rum to sugar-butter-egg mixture.
To serve, preheat broiler.
Pour rum suace over pudding and run under broiler until bubbling.