Bring the milk to a boil in a medium saucepan set over medium high heat.
Reduce the heat to medium. Add the cornstarch, and whisk to combine. Let it boil for 30 seconds-1 minute.
Add the chocolate and whisk until chocolate has melted and completely combined. Let it boil a further 30 seconds or until hot chocolate has thickened into desired consistency.
Pour hot chocolate evenly into four cups and top as desired. Enjoy warm!