Step 1Set the bread cubes on a large baking sheet overnight to dry out. Alternatively, toast them in a 200-degree oven for 30 minutes, then cool to room temperature.
Step 2Melt the chocolate in a medium bowl set over a pot of simmering water, stirring occasionally. When the chocolate is melted, remove from heat and set aside.
Step 3In a large saucepan, whisk together the cream, milk, sugar and vanilla bean (scraped seeds and pod). Bring the mixture to a strong simmer over medium heat. Remove from heat and discard the vanilla pod.
Step 4Whisk the egg yolks in a large bowl. Slowly add the hot cream mixture to the yolks, whisking, to temper the yolks and form a custard base. After the cream mixture is fully incorporated, whisk in the melted chocolate.
Step 5Toss the bread cubes with the custard base to fully coat. Set the mixture aside for 30 minutes, tossing every 10 minutes or so, to allow the cubes to soak in the custard. Meanwhile, heat the oven to 375 degrees.
Step 6Grease a large (9-inch by 5-inch) loaf pan with butter. Gently press the bread and custard mixture into the pan. You might have a little custard or bread or both that will not fit into the loaf pan; discard any leftovers. Loosely cover the pan with foil (butter the underside of the foil so the bread mixture does not stick to it).
Step 7Place the loaf pan in a larger baking pan, and fill baking pan with hot water to cover the sides of the loaf pan by two-thirds.
Step 8Place the baking pan in the oven and bake until the custard is set, about 45 minutes. Serve the bread pudding warm, or cool and reheat before serving. The restaurant cools and slices the bread pudding, then rewarms the slices before serving.
Step 9Serve the pudding with whipped cream and a sprig of mint.