Preheat oven to 350 degrees F. Whisk together the bourbon, milk, sugar, eggs, and vanilla. Pour mixture into a bowl over the cubes of bread and allow bread to soak for 30 minutes. (If mixture is too dry, add a little more milk.) Transfer soaked bread mixture to a buttered 8 by 8 dish. Sprinkle with raisins, cinnamon, and nutmeg and bake for 1 hour, or until golden, puffed up, and crusty on top. Allow pudding to cool to room temperature.
For the Bourbon Sauce: Heat the butter, vanilla, and confectioners' sugar in a saucepan over medium-low heat. When butter is melted and sugar is dissolved, remove from heat and add bourbon. Serve sauce warm over bread pudding.
Recipe courtesy of Colman Andrews, Editor of Saveur Magazine