In a large bowl, whisk together the eggs, milk, heavy cream, granulated sugar, vanilla extract, cinnamon, and salt.
Add the cubed French bread to the mixture, ensuring all bread pieces are well-coated. Let it soak for about 20-30 minutes, occasionally pressing down the bread with a spatula to ensure absorption.
Preheat your oven to 350°F (175°C) and grease a 9x13-inch baking dish.
In a separate bowl, combine the melted butter and brown sugar.
Transfer the soaked bread mixture into the greased baking dish.
Drizzle the butter and brown sugar mixture evenly over the top.
Bake for 45-55 minutes or until the casserole is golden brown and set in the center.
Allow it to cool for a few minutes before serving.