Shred the bread into chunks and put it in a large bowl. Don't worry about the crusts. Pour the milk over the bread and let it sit for an hour. Preheat your oven to 325 degrees. Grease a 9" x 5" loaf pan with 1 tablespoon of the butter. Beat 3 of the eggs in a bowl with a wire whisk. Add the granulated sugar and the vanilla and whisk it some more, until it is light yellow in color. Add this to the bread, and dump in the raisins. Mix it all up with a wooden spoon or a rubber spatula and pour it into the loaf pan. Bake for 45 minutes and let it cool. To make the sauce, melt the butter in a saucepan over low heat. Use a double boiler if you have one (water should be simmering). I don't, but it works anyway. Just keep the heat nice and low so you don't scramble the eggs. Add the powdered sugar and whisk until the sugar is dissolved. Remove from heat and let it cool a little. Beat the remaining egg a bit and add it to the mixture. Add the Bushmill's and whisk it up good. To serve, put a slice of the pudding on an ovenproof plate. Pour some of the sauce over it, and put it under the broiler or in the toaster oven for a minute or so, until it is hot and bubbly. Serve with the remaining booze.