01 - Preheat oven to 350°F. Generously butter a 9x13-inch baking dish to prevent sticking.
02 - Spread bread cubes evenly in the prepared dish. If using raisins, sprinkle them over the bread layer.
03 - In a large bowl, whisk together milk, cream, eggs, sugar, vanilla extract, cinnamon, nutmeg, and salt until fully combined and sugar dissolves.
04 - Pour the custard mixture evenly over the bread, pressing down lightly to ensure all cubes absorb liquid. Let stand for 10 minutes.
05 - Drizzle melted butter over the top. Bake for 40 to 45 minutes until golden brown and set in the center.
06 - While pudding bakes, combine milk, cream, sugar, and butter in a small saucepan. Heat over medium heat, stirring constantly until sugar dissolves and mixture is hot but not boiling.
07 - Mix cornstarch and cold water in a small bowl to make a slurry. Stir into the hot sauce and cook for 2 to 3 minutes, stirring constantly until thickened.
08 - Remove from heat and stir in vanilla extract and salt. Keep warm until serving.
09 - Serve warm bread pudding topped with generous spoonfuls of warm vanilla sauce.