Combine the milk, vanilla bean and vanilla seeds in a saucepan and bring to a simmer. Remove the vanilla bean. Add the hot milk to the blender and carefully blend until frothy. Add the white chocolate to the blender and blend until the chocolate is melted. Divide between 2 mugs, top with a dollop of whipped cream and sprinkle with cocoa powder.
Cook's Note: When blending hot liquids: Remove liquid from the heat and allow to cool for at least 5 minutes. Transfer liquid to a blender or food processor and fill it no more than halfway. If using a blender, release one corner of the lid. This prevents the vacuum effect that creates heat explosions. Place a towel over the top of the machine, pulse a few times then process on high speed until smooth.