Butter an 8-inch square baking dish; set aside. Cut bread in 1/2-inch cubes (makes about 7 cups). In the prepared baking dish, layer half of the bread cubes and half the blueberries; sprinkle with all the cream cheese; cover with remaining bread cubes and blueberries. In a bowl, combine eggs, milk, sugar, salt and cinnamon; pour over bread. Gently press bread down to absorb milk mixture; refrigerate, covered, at least 20 minutes or overnight. Preheat oven to 325°F. Bake uncovered, until a knife inserted near the center comes out clean, about 1 hour; let stand 10 minutes before serving. Slice in 8 rectangles; serve with maple syrup, if desired.