In a medium saucepan, melt the chocolate with two tablespoons of milk on medium heat.Slowly add in the milk, continuously mixing with a wooden spoon.Add in the cocoa powder and sugar, mixing until fully incorporated.In a separate bowl mix the corn starch with one tablespoon of milk, and pour this mixture to the saucepan and mix until the hot chocolate has become thick and coats the back of your spoon.Top with cocoa powder, mini marshmallows or even sea salt.