Pour the whole milk and heavy whipping cream into a medium-sized, heavy-bottomed saucepan. Heat this over medium heat until it's warm and steamy, and you see tiny bubbles forming around the edges. Make sure it doesn't boil, as keeping it just below a boil helps ensure a perfectly smooth, rich texture!
In a small bowl, whisk together the cocoa powder and grated milk chocolate until combined. Take about ½ cup of your warm milk mixture from the saucepan and slowly whisk it into the chocolate powder mix until you have a smooth, lump-free paste. This simple trick is your secret to a silky hot chocolate!
Carefully pour this smooth chocolate paste back into the saucepan with the rest of the warm milk mixture, whisking continuously. Now, add the entire can of sweetened condensed milk and the vanilla extract. Keep whisking until everything is wonderfully combined and super smooth.
Reduce the heat to low and let your hot chocolate gently simmer for 3-5 minutes, stirring frequently. It's ready when it thickens just enough to lightly coat the back of a spoon. If you prefer it thinner, simply stir in a splash more warm milk until it's to your liking.
Ladle this enchanting hot chocolate into your favorite heat-resistant mugs. For an extra special touch, top with a dollop of whipped cream, a delicate sprinkle of ground cinnamon, and some beautiful chocolate shavings. Sip slowly and enjoy every magical, comforting moment!