For the pudding: Slice the panettone into 1-inch cubes to make about 7 cups. Place the cubes in an even layer on a baking sheet to dry out for a few hours or overnight.
In a large mixing bowl, whisk together the milk, brown sugar, egg yolks and vanilla seeds. Add the panettone cubes and mix well with your hands. Let soak for 5 to 10 minutes.
For the meringue: Position the oven rack in the center of the oven and preheat to 350 degrees F. Beat the egg whites with the cream of tartar until stiff peaks form. Gently fold the meringue into the bread pudding mixture, stirring just a few times (you want to see streaks of meringue). Butter a souffle mold and pour in the bread pudding mixture. Bake for 1 hour.
For the creme anglaise: In a medium bowl, whisk together the brown sugar and egg yolks; set aside. Heat the whipping cream and vanilla seeds in a small saucepan over medium heat, stirring constantly. When bubbles form around the edges (about 8 minutes), remove from the heat. Add the vanilla cream to the yolk mixture, 1 tablespoon at a time, whisking constantly. Don't rush things as you don't want to cook the eggs. Pour the mixture back into the saucepan and cook over medium-low heat, stirring constantly and being careful not to let it boil, until the mixture is thick enough to coat the back of a wooden spoon, 3 to 5 minutes. Pass it through a fine-mesh sieve, then pour into a serving container. (If you wish to make this in advance, you can place plastic wrap directly on the surface, pop it in the fridge and it'll keep for up to 2 days. Reheat over low heat.)
Spoon 1 cup warm bread pudding into each serving bowl and add a handful of berries. Drizzle with lots of creme anglaise.