Spray a 9x13 baking dish with non stick spray and set aside.
Chop the bread into 1 inch cubes and add to the baking dish.
Add in the chopped bacon, grated cheese, and diced chives.
In a mixing bowl, whisk together the 9 eggs, milk, dijon mustard, salt and pepper.
Pour the egg mixture over the bread in the baking dish. Press down the bread to ensure it’s all soaked in the egg mixture.
Cover the dish with foil and place in refrigerator to let it soak for at least 30 minutes or overnight.
When ready to bake, preheat oven to 350 degrees F and set the baking dish out to warm up.
Bake covered for 30 minutes, then remove the foil and continue baking another 25 minutes. The top will be golden.
Remove from the oven and allow to sit to cool for 10 minutes before slicing to serve.