Cut the crusty French bread into 1-inch cubes and place them in a greased 9x13 casserole dish.

In a mixing bowl, whisk together the eggs, milk, half and half, granulated sugar, vanilla extract, and cinnamon until smooth.

Pour the egg mixture over the bread cubes, pressing down to ensure all pieces are soaked.

Cover the casserole with plastic wrap and refrigerate overnight, or for at least 2 hours.

In a separate bowl, mix brown sugar, flour, and melted butter until crumbly, then sprinkle over the casserole.

Preheat the oven to 350°F (175°C) about 30 minutes before baking.

Bake for 45-55 minutes until golden and puffed, then let cool for 10 minutes before serving.