Preheat your oven to 350°F and grease a 9x13-inch baking dish with butter.
Spread the bread cubes in the prepared baking dish in an even layer.
In a large bowl, whisk together the eggs, milk, sugar, melted butter, vanilla extract, cinnamon, and salt until smooth and well combined.
If using raisins or chocolate chips, stir them into the egg mixture.
Pour the egg mixture evenly over the bread cubes, pressing down gently with a spatula to make sure all the bread is soaked.
Let the mixture sit for 10 minutes to allow the bread to absorb the custard.
Bake for 40-45 minutes until the top is golden brown and the center is set but still slightly soft.
Let cool for 10 minutes before serving warm with butter, cream, or ice cream if available.