Preheat your oven to 350°F and grease the baking dish with unsalted butter or cooking spray.

Cut the brioche, challah, or French bread into 1-inch cubes and spread them evenly in the prepared baking dish.

In a large bowl, whisk together the eggs, whole milk, sugar, vanilla extract, ground cinnamon, and salt until combined.

Pour the custard mixture over the bread cubes and gently press down to ensure soaking.

Drizzle melted unsalted butter over the top and sprinkle brown sugar if making the Overnight version, or icing for the Cinnamon Roll version.

Allow the casserole to sit for 10-20 minutes, or refrigerate overnight if preparing the Overnight version.

Bake uncovered in the preheated oven for 30-45 minutes, until golden brown and set.

Let cool slightly before slicing and serve warm with maple syrup, powdered sugar, or fresh fruit.