In a medium saucepan, pour in the milk and turn the heat to medium-low. Whisk together cocoa powder and brown sugar into the milk until smooth and well combined.

Continue stirring the mixture constantly as the saucepan warms, watching for steam and tiny bubbles to form around the edges.

Lower the heat slightly and add in semi-sweet chocolate chips. Stir continuously until they melt completely.

Remove from heat and add vanilla extract and a pinch of sea salt, stirring well to combine.

Carefully pour the hot chocolate into mugs, topping with whipped cream or marshmallows as desired.