In a saucepan, heat milk and cream on medium heat until just below simmering point (it should be hot and steamy but not boiling). Remove from heat and add dark and milk chocolate. Let stand for 1 minute, then add vanilla extract and whisk vigorously. Reheat on very low heat (don’t let it boil!) just until chocolate has completely melted and mixture is smooth. Pour into glasses and serve immediately. Alternatively, you can make this a few hours ahead of time and rewarm in a saucepan on low heat just before serving.

Optional: Garnish with cinnamon stick, whipped cream, grated chocolate, or cocoa.