Preheat your oven to 350°F (175°C) and line baking sheets with parchment paper.

Cream softened butter and shortening together until smooth and fluffy.

Add granulated sugar, beating well, then incorporate eggs one at a time along with vanilla extract.

Whisk together the all-purpose flour, cocoa powder, baking soda, and salt in a separate bowl. Gradually combine with wet ingredients until just blended.

Fold in the hot chocolate mix and mini marshmallows into the dough.

Scoop rounded tablespoons of dough onto the baking sheets, spacing them 2 inches apart.

Bake for 10-12 minutes until edges are set and centers are slightly soft.

Cool the cookies on baking sheets for 5 minutes before transferring to a wire rack to cool completely.