In a medium saucepan, pour in whole milk and heavy cream, then set over medium heat. Stir gently for about 3 minutes.

Combine high-quality cocoa powder and grated milk chocolate in a small bowl. Gradually add warm milk from the saucepan to form a smooth paste.

Slowly whisk the chocolate paste back into the saucepan with the steaming milk mixture. Add sweetened condensed milk and vanilla extract, whisk until combined for about 3 minutes.

Reduce heat to low and simmer gently for 3-5 minutes, stirring often until thickened.

Ladle the hot chocolate into mugs, topped with whipped cream and a sprinkle of cinnamon. Serve hot.