Place softened unsalted butter in a large bowl, and beat it with a hand mixer until light and creamy.
Add granulated sugar and beat until light and fluffy.
Add the light brown sugar and beat until light and fluffy.
Add eggs and vanilla extract and beat until well combined.
In a separate bowl, add the flour, hot cocoa mix, baking powder, baking soda, and salt, then whisk everything together until well combined.
Gradually add the dry ingredients to the wet ingredients in several additions, making sure to beat well after each addition. At this point, the dough will be very dry and crumbly.
Add the chocolate chips and dehydrated mini marshmallows. Then, use the hand mixer to begin combining the chocolate chips and marshmallows with the cookie dough.
Once they are slightly combined with the dough, use a plastic spatula or wooden spoon, and begin stirring the dough to continue combining the chocolate chips and marshmallows into the dough.
Then, using your hands, knead the dough to finish combining the chocolate chips and marshmallows. Continue kneading until the dough forms a ball.
Remove the dough from the bowl and wrap in plastic wrap and refrigerate for 24 hours.
After 24 hours, remove the dough from the refrigerator and unwrap it. It will be too hard to use a scoop to portion it out, so cut off pieces with a knife. Then, using your hands, roll the dough into balls the size of golf balls.
Place eight balls of dough, two inches apart, onto a parchment lined large rimmed baking sheet.
Place several chocolate chips and mini dehydrated marshmallows onto the top of the dough balls and then flatten the balls a little with the palm of your hand.
Bake the cookies in a 350°F oven for 12 minutes. Remove from the oven and let the pan cool on a wire rack for about five minutes.
Transfer the cookies from the pan to the wire rack and allow them to continue to cool.
Yield 24 cookies.