Preheat oven to 350°F (175°C) and grease an 8-inch square baking dish with butter or non-stick spray.

In a medium saucepan, combine whole milk, granulated sugar, unsalted butter, ground cinnamon, and fine sea salt over medium heat, stirring continuously for about 5 minutes until the mixture is steaming.

Tear stale bread into bite-sized cubes and place them evenly in the greased baking dish.

In a separate bowl, whisk the eggs until well beaten, then gradually whisk in the cool milk mixture and pure vanilla extract.

Pour the custard mixture over the bread cubes, gently pressing down with a spatula to ensure every piece is coated. Let it soak for 20-30 minutes.

Bake the pudding for about 40-45 minutes until the top is golden brown and a knife inserted comes out clean.

While the pudding bakes, prepare the vanilla sauce by heating together whole milk, heavy cream, light brown sugar, and unsalted butter until steaming.

In a small bowl, dissolve cornstarch in water or optional bourbon, then whisk it into the steaming milk mixture and cook for an additional 2-3 minutes until thickened.

Serve the baked pudding warm, drizzled with the vanilla sauce.