In a medium saucepan, combine milk, cacao powder and sugar. Whisk until smooth. Bring the mixture to a slow simmer on medium-low flame, about 4~6 minutes. Turn off the heat and stir in vanilla extract.
Pour into mugs and serve right away with an optional dollop of whipped cream and sprinkle with cocoa powder.
I recommend using raw cacao powder for the gives the most rich chocolaty flavor to the hot cocoa. But you can definitely make it with regular cocoa powder. Find the best quality unsweetened cocoa powder you can find.
I use 2% milk to make this hot cocoa. But if you only have whole milk on hand, then go ahead and use it.
If you want to make vegan hot cocoa, then I recommend using unsweetened oat or almond milk.
You can sweeten this hot chocolate with white sugar or use maple syrup or agave nectar.
Make this hot cocoa just before serving. But you also make it ahead of time, cool completely and store in the fridge. Warm it until heated through right before serving.