Preheat your oven to 350°F (175°C).
Grease your baking dish with melted butter.
Cut the bread into 1-inch cubes and place them evenly in the prepared baking dish.
In a large mixing bowl, whisk together the eggs, milk, heavy cream, granulated sugar, vanilla extract, ground cinnamon, and salt until well combined.
Pour the custard mixture over the bread cubes, making sure all pieces are evenly soaked, and gently press down on the bread to help it absorb the custard.
Cover the dish with plastic wrap or aluminum foil and refrigerate for at least 30 minutes (or up to overnight for best results).
Remove the cover from the baking dish and bake in the preheated oven for about 45 minutes, or until the top is golden brown and a toothpick inserted in the center comes out clean.
Let the casserole cool for a few minutes before serving. Dust with powdered sugar and serve with maple syrup or fresh fruit, if desired.
For added flavor, consider mixing in some fruit such as berries or bananas between the layers of bread before pouring the custard.
Store any leftovers in the refrigerator and reheat in the microwave or oven.