Heat the milk and sugar in a small saucepan over medium heat until it is hot. Do not let it boil. Put the white chocolate into a mug, add the hot milk, and stir vigorously. Add the liqueurs and stir gently. (Or, if available, place all the ingredients into a pitcher and steam with an espresso wand.) Serve immediately.
Slice the vanilla bean in half lengthwise. Scrape out the seeds and place them along with the bean rind into an airtight container along with the sugar. Mix thoroughly. Let sit for 1 week before using.