Grease a 9x13 inch baking dish, and set it aside.

Cut the day-old French bread or brioche into 1-inch cubes, and place them in a single layer in the prepared baking dish.

In a mixing bowl, whisk together the milk, granulated sugar, pumpkin puree, eggs, vanilla extract, and pumpkin pie spice (or cinnamon). Mix until well combined.

Pour the mixture evenly over the bread cubes in the baking dish, making sure all the bread is soaked. Press down lightly to ensure even soaking.

In a separate bowl, prepare the streusel topping. Combine the light brown sugar, all-purpose flour, diced cold butter, chopped pecans, and cinnamon spice. Use a pastry cutter or your fingers to blend the mixture until it forms a crumbly texture.

Sprinkle the streusel topping evenly over the bread mixture in the baking dish.

Cover the baking dish with foil, and let it sit in the refrigerator for at least 2 hours or overnight. This allows the bread to absorb the liquid and flavors.

To bake, preheat the oven to 350 degrees Fahrenheit (175 degrees Celsius).

Bake the French Toast Casserole, covered with foil, for 30 minutes.

Then, remove the foil, and bake for an additional 15-20 minutes or until the top is golden brown and the casserole is set.

Let it cool for a few minutes before serving. Drizzle with maple syrup or sprinkle with powdered sugar, if desired.