Preheat your oven to 350°F (175°C).
Cube the loaf of French bread into 1-inch pieces and place them in a large mixing bowl.
In another bowl, whisk together the eggs, milk, heavy cream, sugar, vanilla extract, cinnamon, and salt until smooth.
Pour the custard over the cubed bread and gently fold to combine, ensuring every piece is moistened.
Cover the bowl with plastic wrap and refrigerate for at least 1 hour, or overnight if possible.
Grease a 9x13-inch baking dish with butter or cooking spray.
Transfer the soaked bread to the prepared baking dish, spreading it evenly.
Bake the casserole in the preheated oven for 40-50 minutes, or until the top is golden brown and a knife inserted in the center comes out clean.
Let the casserole cool for a few minutes before serving.
Serve warm with maple syrup, fresh berries, or a sprinkle of powdered sugar, if desired.