Preheat oven to 350 F.
Cut the bread slices in half and spread with butter.
In a small bowl, combine sugar and cinnamon and mix well.
In a square casserole dish, place half of the bread slices, buttered side up.
Sprinkle the top liberally with half of the cinnamon sugar and melted chocolate.
Add the remaining bread slices on top.
Sprinkle with the remaining cinnamon sugar and melted chocolate.
In a saucepan, combine the milk and cream until warm, but not boiling.
Meanwhile, beat the eggs until light and airy. Add vanilla extract and beat well.
Slowly add the heated milk to the eggs, while whisking constantly to avoid the eggs cooking.
Pour this custard mix over the prepared bread in the casserole dish. Let it sit for 5 minutes.
With a rubber spatula, press down on the bread slices so that the liquid will rise to cover the bread slices. Let it sit for another 5 minutes.
Bake in prepared oven for 40 minutes.