In a large bowl, cream butter and both types of sugar until the mixture is smooth and fluffy.
Beat in the eggs one at a time, ensuring each is fully incorporated before adding the next. Add the vanilla extract after mixing in the eggs.
In a separate bowl, whisk together the flour, hot chocolate mix, salt, baking powder, and baking soda.
Gradually add the dry ingredients to the wet ingredients, mixing until fully incorporated.
Fold in the milk chocolate chips, semi-sweet chocolate chips, and mini marshmallows.
If time allows, chill the dough in the refrigerator for 30 minutes.
Preheat your oven to 350 degrees F (175 degrees C) and line your baking sheets with parchment paper.
Using a cookie scoop or your hands, form the dough into balls about 1½ tablespoons each.
Bake the cookies for 8 to 10 minutes, or until the edges are golden brown but the centers look soft.
After baking, allow the cookies to cool on the baking sheet for about 5 minutes before transferring them to a wire rack.
