Preheat the oven to 350F degrees. Spray a 9"x13" baking dish with non-stick cooking spray, set aside.
Cut bread into 1"-2" squares and add to a large bowl.
In another bowl whisk together the milk, heavy cream, eggs, sugar, hot chocolate powder and vanilla, until combined.
Pour this milk mixture over the bread and stir gently to coat, let soak for about 20 minutes.
Spread bread mixture into prepared baking dish and bake in oven for about 50-60 minutes until center is set. Remove and let cool.
For the marshmallow sauce:
In a medium bowl beat together the marshmallow fluff and powdered sugar until combined.
Slowly drizzle in the heavy cream until you get to the desired consistency.
Pour on individual slices or over whole bread pudding.
Notes
Feel free to use any thick bread: Challah bread, French bread, Italian loaf, or thick sliced white bread (like Texas toast).
Want a more sweet and salty flavor? Try drizzling the top of each slice with SALTED CARAMEL rather than the marshmallow cream sauce.
Don't rush the process. The bread needs time to soak up the custard sauce before you bake it. If necessary, stir the bread as it soaks in the custard to make sure all the bread pieces get a good soaking. It makes all the difference!