Place raisins in small bowl and soak in Rum. In large mixing bowl, combine milk, cream, eggs, sugar, and raisins. Break bread into the bowl and fold the mixture until the bread is soggy. Butter a large 9 x 13" pan and pour in the bread mixture. Push 6 tablespoons of butter into the top of the loaf and set pan in a large pan filled with about 1/2" of water. Bake bread pudding in water bath for 30 minutes; then remove from bath and bake for another 45 minutes. Slice the bread pudding and serve warm topped with Rum sauce (recipe below). You can add one cup chopped pecans, if desired.
Rum Sauce: 3 large eggs, 1 c. sugar, 1 teaspoon vanilla, 1/2 cup milk, 1 tablespoon cornstarch, 1/4 cup cold water, 3 tablespoons light Rum.
Place eggs in a large saucepan and whisk over medium heat until slightly thickened. Add sugar, vanilla and milk and cook until hot; DO NOT let mixture boil. In small bowl, blend the cornstarch into cold water. Stir cornstarch into the egg mixture, stirring constantly. Add rum and cook over medium heat until smooth and thick enough to coat the back of a spoon; about 15 minutes, stirring constantly.