Preheat your oven to 350°F, and grease one 9x13-inch brownie pan with butter.
Spread the brioche bread cubes (650g) over a large baking pan lines with parchment paper, and toast in the oven for 10 minutes mixing at the 5 minutes mark.
Remove from the oven and set a side to cool.
Beat the eggs (4) and egg yolks (4) in a medium bowl and set aside.
Pour the heavy cream (600ml), milk (480ml), light brown sugar (100g), and two cinnamon sticks in a medium sauce pan and briong to a boil.
Remove from the stove and pour into a large measuring cup. Set aside to cool until warm and nice to the touch (about 90-95°F).
Pour the melted white chocolate into the milk mixture and mix until smooth.
Add the eggs mixture and mix until smooth.
Place the bread cubes in a large mixing bowl, then pour over the wet mixture.
Use a knife or a spatula to gently dip the bread pieces that are out of the custard. Set it aside for 15 minutes to allow the bread to soak in the cistard.
Preheat your oven to 320°F.
Use a slotted spoon to remove the bread from the bowl and tranfer it to the prepared pan.
Pour over any custard leftover, and bake over the middle oven rack for 45-55 minutes. The pudding is ready when the sides (1-inch away from the sides of the pan) is set and the center is puffed but not set all the way (some liquids is ok).
Remove from the oven and set it aside to chill and set for about 1-2 hours before serving.
Refrigerate covered with a plastic wrap and aluminum foil or an airtight container for up to 5 days.
Allow the bread pudding to chill for at least two hours before serving, it will give it enough time to set as well as develop all the flavors.
Notes
Use milk, or dark chocolate instead of white chocolate for chocolate bread pudding.
Sprinkle the top with chopped nuts, chocolate chips or even raisins for more flavor and texture.
Make it the night before and bake it the next day for a make ahead.