Place cream, 1 cup milk, the split and scraped vanilla bean and sugar in a medium cooking pot.
Place over medium high heat and, stirring, bring to a boil. Reduce heat to a simmer.
In a small bowl, whisk together remaining cup of milk, eggs and egg yolks.
Gently melt 4 ounces bittersweet chocolate over barely simmering water.
Gradually whisk a small amount, 1 to 2 tablespoons, of the hot cream mixture into the egg mixture.
Repeat with another 1 to 2 tablespoons hot cream mixture.
Then whisk egg mix into the remaining hot cream mixture.
Gradually whisk about 1 cup of this egg/cream mixture into melted chocolate.
Finally whisk melted chocolate mixture into remaining hot liquid.
Add the vanilla extract. Mix well with the whisk.
Place bread cubes in a large bowl.
Pour all chocolate liquid over the small bread cubes. Whisk to combine and to break up the bread pieces.
Pour mixture into buttered 9 X 13-inch pan.
Sprinkle top with remaining milk and bittersweet chocolate pieces.
Preheat oven to 325°F.
Place pan in preheated oven and bake for about 45 to 55 minutes until set.
Serve warm.