Add milk, heavy cream, and brown sugar to a pan and cook on medium heat until the milk comes to a boil.
Add cocoa powder, and chocolate chips and cook until the chocolate chips dissolve and the hot chocolate is thick and creamy. Stir very frequently while cooking.
Add vanilla extract.
Finally, add bourbon and mix well.
Pour the hot chocolate into serving mugs. Garnish with whipped cream, marshmallows, and a sprinkling of ground cinnamon, and serve immediately.