In a medium saucepan, combine 2–3 cups of whole milk with ½ cup of heavy whipping cream. Place over medium heat and warm for about 5–7 minutes, stirring occasionally.

In a small bowl, whisk together ½ cup of cocoa powder and ½ cup of grated chocolate. Gradually add about ½ cup of the warm milk mixture to the cocoa blend, whisking continuously until smooth.

Pour the chocolate mixture back into the saucepan with the remaining milk, and add sweetened condensed milk along with ⅛ teaspoon of vanilla extract. Stir until well incorporated.

Turn heat down to low and allow to simmer for about 3–5 minutes, stirring frequently until thickened.

Ladle the hot chocolate into mugs, topping with whipped cream and a sprinkle of cinnamon or cocoa powder if desired.