In a medium saucepan, combine 2–3 cups of whole milk and ½ cup of heavy cream. Heat until it steams but does not boil, approximately 5–7 minutes.

In a small bowl, whisk together ½ cup of cocoa powder and 1-2 tablespoons of grated milk chocolate, then mix in about ½ cup of hot milk mixture until smooth.

Gradually pour the chocolate paste back into the saucepan with the hot milk. Whisk in the can of sweetened condensed milk and ⅛ teaspoon of vanilla extract.

Reduce heat to low and let simmer for about 3–5 minutes, stirring frequently, until it thickens.

Pour into mugs and top with whipped cream, ground cinnamon, and chocolate shavings if desired.