Arrange the bread cubes in a single layer on a cookie sheet fitted with a wire rack. Preheat the oven to 225° F. Bake for 30 minutes. Allow to cool.
Heat heavy cream and milk in a medium saucepan over low heat until simmering. Place chopped chocolate in a medium bowl and add the simmering milk and cream. Allow to rest for a few minutes to let the chocolate melt then whisk until combined. Allow the mixture to cool slightly to avoid ruining the eggs in the next step.
Whisk together the eggs, sugar vanilla extract, vanilla bean seeds, cocoa powder and salt until smooth. Slowly add the chocolate cream mixture (in a slow drizzle) while whisking the mixture. Remove ⅓ of this mixture and set aside. Add the bread cubes to the remaining mixture and stir to coat.
Grease a 12” cast iron skillet or 9 X 13 pan. Add the chocolate bread mixture to the skillet and spread evenly. Pour the reserved chocolate mixture over the top. Cover and allow to rest at room temperature for 40 minutes. This allows the chocolate to soak through all of the bread. Otherwise, the finished bread pudding will have white spots where the chocolate did not soak in.
Preheat the smoker to 350°F (using charcoal but no wood chips) or preheat the oven to 350°F. Cover the bread pudding loosely with foil and bake for 30 minutes. Remove the foil and continue to bake for another 15 - 20 minutes. It will be done when a toothpick inserted is mostly dry, not wet, and the top is somewhat crisp. Allow to rest 5 minutes before serving.
Heat sugar in a medium saucepan over medium-low heat stirring constantly. When the sugar has melted, add the butter and stir constantly until combined. Cook 1 minute without stirring, then add the heavy cream. Stir to combine. Cook for 1 minute then remove from heat. Stir in the salt and allow to cool for a few minutes. Serve over hot bread pudding.