Begin by cutting the French bread into approximately 1-inch cubes. Arrange these cubes evenly in a generously greased 9x13 baking dish.

In a large mixing bowl, whisk together the eggs, whole milk, heavy cream, brown sugar, vanilla extract, and cinnamon until fully combined and smooth.

Pour the custard mixture over the arranged bread cubes, ensuring every piece is thoroughly soaked in the creamy goodness.

Cover the baking dish tightly with plastic wrap or aluminum foil and place it in the refrigerator for at least 6 hours, or overnight if possible.

Preheat your oven to 350°F (175°C) and bake for about 55 minutes, or until the top is golden brown and slightly puffed.

Allow the casserole to cool for a few minutes before serving. Dust the top with powdered sugar and serve warm with maple syrup or fresh berries.