Preheat oven to 350° and butter a large baking dish (I used 14 x 11 1/2 x 2 1/4).
Slice bread and then cut into 1" cubes.
Place 1/2 of bread cubes into baking dish.
In a large mixing bowl, whisk milk, eggs, sugar and vanilla together and pour one cup over bread.
Next, add sliced bananas and walnuts on top of bread then add the remaining bread to the baking dish.
Pour the rest of the milk mixture over the bread making sure all pieces of bread have been soaked.
Cover with foil and place in the oven. Bake for 1 hour then remove foil and pop back into the oven for 20 more minutes.
Remove from oven. Let cool for 10 minutes or so.
Serve warm and enjoy!