In a large mixing bowl, whisk together 8 large eggs, 2 cups of milk, 1 cup of brown sugar, 1 tablespoon of vanilla extract, 1 teaspoon of cinnamon, and a pinch of salt until smooth and well combined.

Cut 1 loaf of stale French bread into 1-inch cubes and gently toss them into the egg mixture.

Grease a 9x13-inch casserole dish with butter or cooking spray and transfer the soaked bread mixture into the dish, spreading it out evenly.

In a medium bowl, mix together 1 cup of brown sugar, 1 cup of flour, and 1 teaspoon of cinnamon. Cut in 4 tablespoons of cold butter until the mixture resembles coarse crumbs.

Sprinkle the streusel topping evenly over the bread mixture in the casserole dish. Place the dish in the preheated oven and bake for 45-50 minutes, or until set and golden brown.

Once baked, remove the casserole from the oven and let it cool for a few minutes before serving warm.