Preheat the oven to 175 degrees C.
Break the bread into small pieces and place it in an 8-inch square baking pan. Drizzle melted butter or margarine on top of the bread. Sprinkle with chocolate chips if desired.
Combine the eggs, milk, sugar, cinnamon, and vanilla in a medium mixing bowl. Mix until everything is well combined. Pour over the bread and gently press down with a fork until the bread is covered and soaking up the egg mixture.
Bake for 45 minutes in the preheated oven or until the top springs back when lightly tapped.