How can I make my Hot chocolate thicker? I've been trying to make a thicker hot chocolate and I'm not sure what to add without taking away from the flavor of the chocolate. Usually what I do is boil the milk, and then I add chocolate baking powder and shaved chocolate.
Spanish hot chocolate and Italian cioccolata fiorentina both use cornstarch as a thickening agent. Both are used more for dipping or sipping (churros in the former case), however you could easily just use less cornstarch to make it more 'drinkable'. 

Try a teaspoon of cornstarch, mixed with a little cold water, added to the milk when you boil it.

As Kate Gregory suggests, you could also use full-fat milk, or loads of shaved chocolate.