Peel the sunchokes (yes, their gnarly shape makes this task somewhat tedious...), and cut them up. Split the vanilla bean.
In a large pot or Dutch oven, melt the shallot over medium-heat (don’t let it brown). Then, place the sunchokes in the pot, and cover with hot water so that the water level is 2 inches above the sunchokes (about six cups of water).
Scrape the seeds of the vanilla bean and stir them into the water, place the bean in there too.
Cover, bring to a boil, lower heat and let simmer about 25 minutes, until the sunchokes are tender (test with a knife like you would a potato).
Remove the vanilla bean, and mix the soup with an immersion blender or in a blender until very smooth. Add in the chestnut puree, coconut milk and truffle oil, and blend again. Add salt and pepper to taste. (Can be made ahead up to this point, and refrigerated for up to 2 days).
Reheat gently over low heat before serving. Serve in bowls, with a twist of freshly ground pepper on top, and a drizzle of truffle oil, if you're so inclined.