Butter a glass 9 x 13 baking dish. Cut french bread into cubes and spread out into pan.
In a medium bowl, whisk together egg nog, half n half, eggs, sugar, vanilla and cinnamon. Pour mixture over bread, then cover and chill for 2 hours, or overnight if preferred.
Preheat oven to 350 degrees. In a small bowl, mix together with a fork, brown sugar, flour and cinnamon. Add in butter and mix to form the crumbled topping. Sprinkle on top of prepared bread.
Cover with foil and bake for approximately 20 minutes. Uncover and bake an additional 20 minutes or until golden brown. Test for doneness by inserting a toothpick in the center, to check that eggs have fully cooked.
Remove from oven and let sit for 5 minutes. Mix icing ingredients, egg nog and powdered sugar to a thin consistency. Add a few drops more egg nog as needed. Drizzle on top of casserole, and sprinkle with fresh blueberries.
Slice into squares, and top with whipped cream. Serve immediately. Refrigerate any leftovers.
There is no Nutrition Label for this recipe yet.
If bread is too soft, toast in the oven at 200 degrees for 10 minutes before cutting.