01 -
Using your stand or handheld mixer with paddle attachment, whip the butter with both sugars at medium-high until it's airy and pale, around 2-3 minutes. Drop in the egg and vanilla, then beat everything until it comes together. Don't forget to scrape down the bowl sides when needed.
02 -
Mix flour, cocoa powder, hot cocoa mix, baking soda and salt in another bowl with a whisk. Slowly add this dry mix to your wet ingredients while mixing on low. Pour in the milk last. Your dough will turn out pretty thick and sticky.
03 -
Wrap the dough tightly and stick it in the fridge for at least 2 hours but you can leave it up to 3 days. Don't skip chilling - it'll help manage the stickiness.
04 -
Get your oven hot at 177°C (350°F). Put parchment or silicone mats on your baking sheets.
05 -
Roll dough into balls weighing about 25-26g each (that's a big tablespoon). Space them 2-3 inches apart on your lined sheets. Bake for just 10 minutes, then pull them out.
06 -
Stick half a marshmallow on top of each warm cookie and pop them back in the oven for 2 more minutes. After taking them out, gently flatten each marshmallow with the back of a spoon.
07 -
Let the cookies sit on the baking sheet for 10 minutes before moving them to a wire rack to cool all the way.
08 -
Melt your chocolate chunks using either a double boiler or microwave. For microwave melting, go with 20-second bursts, stirring between each until it's smooth. Drizzle the melted chocolate over your cooled cookies.
09 -
Let cookies sit at room temp for 30-60 minutes so the chocolate can harden. Once firm, they're ready for stacking, storing or giving away.