Step 1Heat the half-and-half with the sugar and the vanilla bean in a medium saucepan over high heat. Once it reaches a boil, remove from heat. Pour the buttermilk into a metal bowl and set the bowl over the half-and-half for 15 minutes to remove the chill. Meanwhile, stir the gelatin into the cold water and set aside for 5 minutes to soften.
Step 2Remove the bowl of buttermilk from over the half-and-half. Take the vanilla bean out and scrape the seeds back in, reserving the pod to make vanilla sugar, if desired.
Step 3Heat the half-and-half once again until it comes to a near boil, then remove from heat. Stir in the softened gelatin until it's completely dissolved, then whisk in the buttermilk. Pour the mixture into 6 juice glasses and refrigerate until set, about 3 hours.