Lightly grease a large baking dish (9 x 13″) with butter or oil and pre-heat the oven to 375 degrees Fahrenheit.
In a large bowl, whisk together the milk, eggs, vanilla, maple syrup, cinnamon, nutmeg, and salt, and set aside so that everything marries together and activates, about 5 minutes.
Next, add the chopped bread into the prepared baking dish and spread around evenly.
Pour the liquid mixture atop bread, generously covering all pieces. Add blueberries, tucking them in between the bread as much as possible.
Bake casserole for 35-40 minutes or until fully cooked through (less 'jiggly') and edges and tops are golden brown (or slightly dark brown, if preferred).