Grease the baking pan or casserole dish with the melted butter.
Tear the bread into chunks, or cut into cubes, and distribute evenly in the pan.
If you are adding the optional 1/3 cup of sultanas, raisins or dried cranberries scatter them in at this point.
Crack the eggs in a big bowl.
Whisk together the eggs, milk, cream, sugar of choice, and vanilla.
Pour evenly over the bread.
Cover the pan/dish tightly and allow to sit overnight in the refrigerator.