Preheat your oven to 350°F (175°C).
Place the bread cubes in a greased baking dish.
In a mixing bowl, whisk together the milk, sugar, cinnamon, beaten eggs, vanilla extract, and melted butter until well combined.
Pour the milk mixture over the bread cubes, ensuring all pieces are well-coated. Allow the bread to soak for about 10 minutes.
If using raisins, sprinkle them evenly over the soaked bread mixture.
Bake in the preheated oven for 45 minutes, or until the top is golden brown and a knife inserted into the center comes out clean.
Remove from oven and let cool slightly before serving. Enjoy warm, possibly with a scoop of ice cream or a drizzle of caramel sauce!