Split the vanilla bean lengthwise and scrape out the seeds with a knife. Place both the seeds and the pod into the milk.
In a saucepan, bring the milk with the vanilla to a boil. Cover and let it infuse for a few minutes. Then, remove the vanilla pod.
Using a whisk, incorporate the 70% dark chocolate into the hot milk until fully melted and smooth.
Depending on your taste, you can continue cooking the hot chocolate. The longer you cook it, the thicker and more velvety it will become.
Pour the hot chocolate into your chosen cups or mugs. Serve with whipped cream on the side or on top.
Notes
To make 200g (about 1 cup) of whipped cream, you only need 100ml (about 1/2 cup) of heavy liquid cream. Whip the cream vigorously until soft peaks form, and it becomes light and fluffy.