In a large mixing bowl, beat butter, granulated sugar, and brown sugar until light and fluffy.
Add eggs and vanilla extract, mixing until fully combined.
In a separate bowl, whisk together flour, hot chocolate mix, salt, baking soda, and baking powder.
Gradually stir the dry ingredients into the butter mixture until just combined.
Fold in milk chocolate chips and marshmallow bits.
Cover and refrigerate the dough for at least 4 hours.
Preheat oven to 350°F and line baking sheets with parchment paper.
Scoop 1 ½-inch balls of dough and place 2–3 inches apart on the prepared sheets.
Press a few extra chocolate chips and marshmallow bits into the tops, if desired.
Bake for 9–11 minutes, until edges are golden and centers appear slightly soft.
Cool on the baking sheet for 5 minutes before transferring to a wire rack. Serve and enjoy!