In a medium saucepan, combine 2-3 cups of whole milk and ½ cup of heavy whipping cream. Heat the mixture over medium heat, stirring occasionally until it becomes steaming but not boiling, about 5-7 minutes.

While the milk is heating, whisk together ½ cup of high-quality cocoa powder and 1-2 tablespoons of grated milk chocolate in a small bowl. Gradually add about ½ cup of the hot milk mixture and whisk until smooth.

Pour the smooth chocolate mixture back into the saucepan with the remaining hot milk. Whisk while adding 1 can of sweetened condensed milk and ⅛ teaspoon of vanilla extract.

Reduce heat to low and simmer for 3-5 minutes, stirring frequently until thickened. Adjust thickness with warm milk if needed.

Ladle into mugs and top with whipped cream and a sprinkle of cinnamon or chocolate shavings. Serve immediately.