Creating this delicious Blueberry French Toast Casserole is straightforward. Follow these simple steps for success:

1. Prepare the Baking Dish: Preheat your oven to 350°F (175°C). Grease a 9×13-inch baking dish with butter.
2. Cube the Bread: Cut the French bread into 1-inch cubes and place them evenly in the prepared baking dish.
3. Add Blueberries: Gently sprinkle the fresh blueberries over the bread cubes, distributing them evenly.
4. Make the Custard Mixture: In a large mixing bowl, whisk together the eggs, milk, sugar, vanilla extract, cinnamon, and salt until smooth and well combined.
5. Combine: Pour the custard mixture over the bread and blueberries, ensuring all bread pieces are soaked.
6. Soak: Allow the mixture to sit for a few minutes so the bread absorbs the liquid. For best results, cover and refrigerate for at least 30 minutes or overnight.
7. Bake the Casserole: Place the casserole in the preheated oven and bake for 35-45 minutes, or until it’s puffed and golden brown.
8. Check for Doneness: A toothpick inserted in the center should come out clean. If it is not yet set, return it to the oven and check every 5 minutes.
9. Cool: Once baked, remove the casserole from the oven and allow it to cool for 10-15 minutes before serving.
10. Serve: Dust with powdered sugar if desired, and serve warm with maple syrup on the side.

With these clear steps, anyone can successfully create this remarkable casserole effortlessly.