Remove crusts from bread; cut bread into cubes. You should have about 6 cups (1.5 L). Reserve in a a large bowl. In a medium bowl, place white chocolate. Pour hot milk over chocolate; allow to rest 5 minutes. Whisk until smooth. In a large bowl, whisk eggs with sugar and vanilla; beat in milk mixture. Pour over bread cubes. Cover and refrigerate at least 2 hours. Butter a 4 quart (2 L) baking dish or casserole. Spoon bread and custard into baking dish. Press pieces of chocolate into the bread evenly. Bake, uncovered, in a preheated 350 F (180C) oven for about 40 to 45 minutes or until puffed and set. Cool at least 15 minutes before serving.