How to Make It
Preheat the oven to 375°. Butter a 9-inch-square glass or ceramic baking dish. In a large bowl, whisk the milk with the vanilla. Add the bread, submerge it in the milk and let stand for 5 minutes.
In a bowl, whisk the eggs and sugar until pale and fluffy. Add to the soaked bread and stir; fold in the blueberries. Transfer to the prepared baking dish and poke the chocolate half way into the pudding. Dot the pudding with the butter and bake for 45 minutes, or until the pudding is browned and crisp. Let stand for 10 minutes before serving.