Step 1

Fill a small pot with the water and bring to a boil. Whisk in the cocoa powder and sugar.

Step 2

Reduce heat to medium and whisk in the milk. Cook over medium heat until the milk is heated but not boiling, about 3 minutes

Step 3

Add chocolate chips and continue to whisk until the chocolate chips melt and the mixture becomes smooth, about 2 more minutes.

Step 4

Remove from the heat; stir in vanilla extract.

Step 5

Serve with mini marshmallows, if desired.