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

While the milk mixture heats, whisk together ½ cup of cocoa powder and 1–2 tablespoons of grated milk chocolate in a separate bowl. Add about ½ cup of the hot milk mixture, stirring until smooth.

Pour the chocolate mixture back into the saucepan with the remaining hot milk, whisking continuously to blend evenly.

Stir in ½ cup of sweetened condensed milk and 1 teaspoon of vanilla extract, whisking until combined.

Lower the heat and simmer for 3–5 minutes, stirring frequently until thick enough to coat the back of a spoon.

Once thickened, remove from heat, pour into mugs, and garnish with whipped cream, ground cinnamon, and chocolate shavings.