In a medium saucepan, heat the milk over medium heat until it is warm but not boiling. Stir frequently to prevent scorching.
4 cups Milk
Add the chopped Mexican chocolate, granulated sugar, ground cinnamon, and cayenne pepper to the warm milk. Whisk until the chocolate is completely melted and the mixture is smooth.
4 cups Milk
Continue to heat the mixture, whisking occasionally, until it is hot and slightly frothy. Do not boil.
Remove from heat and stir in the vanilla extract.
4 cups Milk
Pour the hot chocolate into mugs and serve immediately. Optional garnishes include whipped cream, cinnamon sticks, or a pinch of chili powder.
Notes
Adjust the amount of sugar and cayenne pepper to your personal taste. For a richer flavor, you can use dark chocolate instead of Mexican chocolate.