Preheat oven to 350*. Pile the bread cubes on a baking sheet and toast them in the oven for about 15 minutes. Remove them from the oven and let them cool a bit. You want them to dry out a bit before mixing them with the custard so that they absorb as much of the liquid as possible. Raise the oven temperature to 375*. While the bread is toasting, put the chocolate pieces in a microwave-safe bowl. Microwave the chocolate on high for 1 minute, let it rest, then heat it for 1 min more. Remove the chocolate and stir it with a spatula or spoon until it is smooth and melted. In a very large bowl, mix together the eggs, cream, milk, half and half, sugar and spices. Add the melted chocolate and whisk until the mixture is smooth. Put the bread in the bowl, toss well and let the bread soak in the custard mixture at least half an hour and up to two hours, tossing occasionally to make sure all the bread cubes are well coated. Spray a very large baking pan (or 2 medium baking pans) with cooking spray. Turn the bread-custard mixture into the pan(s) and smooth out the top. Bake at 375* for 45 minutes to an hour, until the pudding is set. Remove the pudding from the oven and let it sit at least 15 minutes before serving. Serve hot, warm or at room temperature with whipped cream.