01 - Preheat oven to 350°F. Grease a 9x13-inch baking dish with butter or cooking spray.
02 - Place bread cubes in a large mixing bowl.
03 - In a separate bowl, whisk together milk, cream, eggs, sugar, vanilla extract, cinnamon, nutmeg, and salt until the mixture is smooth and well combined.
04 - Pour the custard mixture over the bread cubes. Add raisins and gently mix, pressing the bread down to ensure thorough saturation. Allow the mixture to rest for 10 minutes.
05 - Pour the bread and custard mixture into the prepared baking dish. Drizzle melted butter evenly over the top.
06 - Bake for 45 to 50 minutes, until the pudding is set and the top is golden brown.
07 - While the pudding bakes, melt butter in a saucepan over low heat. Whisk in powdered sugar until the mixture is smooth.
08 - In a small bowl, beat the egg. Slowly whisk the beaten egg into the butter-sugar mixture, stirring continuously over low heat until thickened, approximately 2 to 3 minutes.
09 - Remove the saucepan from heat. Stir in bourbon or vanilla extract according to preference.
10 - Transfer warm bread pudding to serving plates or bowls. Drizzle bourbon sauce generously over each serving.