In a medium saucepan, combine dry ingredients and whisk to combine.
Add a few tablespoons of the whole milk and whisk again to form a paste. This will ensure that when you add the rest of the milk, there are no lumps of dry ingredients.
Once smooth, add the chocolate and the rest of the milk.
Place over medium hit and whisk continuously to ensure that the chocolate melts evenly.
If you prefer your hot chocolate thinner, you can stop here.
The cornstarch will thicken as it cooks so for a very thick hot chocolate bring the mixture to a boil stirring constantly. Remove from heat and pour into mugs.