01 - Preheat oven to 350°F. Grease a 2-quart baking dish with butter to prevent sticking.
02 - Distribute bread cubes evenly across the bottom of the prepared dish.
03 - In a large mixing bowl, vigorously whisk the whole milk, heavy cream, eggs, granulated sugar, vanilla extract, ground cinnamon, and salt until smooth and homogeneous.
04 - Pour the custard mixture evenly over the bread cubes. Gently press the bread into the liquid so all pieces absorb the custard. Allow mixture to rest for 10 to 15 minutes.
05 - If desired, drizzle melted butter over the top and sprinkle evenly with light brown sugar.
06 - Bake uncovered for 40 to 45 minutes, or until fully set and the surface is golden brown.
07 - Remove from oven, allow to cool slightly, then portion and serve warm. Garnish with whipped cream or powdered sugar if desired.