In a large bowl, whisk together eggs, milk, cream, brown sugar, vanilla, cinnamon, and salt.
Grease a 9×13 baking dish and spread the cubed bread evenly.
Prepare another pan with aluminum foil or parchment to catch the excess. It is super sticky and hard to clean off the oven.
Pour the custard mixture over the bread, pressing down lightly so all the pieces soak it up.
Cover the dish and refrigerate overnight.
In the morning, preheat oven to 350°F. Let the casserole come to room temperature.
Bake covered with foil for 30 minutes, then uncover and bake an additional 20–25 minutes until golden and puffed.
Drizzle with melted butter and dust with powdered sugar before serving.
Serve warm with fresh berries or maple syrup if desired.
