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

In a stand mixer, cream together butter, granulated sugar, and brown sugar until light and fluffy, about 2-3 minutes.

Mix in the egg, milk, and vanilla extract until well combined.

In a separate bowl, whisk together flour, hot cocoa mix, unsweetened cocoa powder, baking soda, and salt. Gradually incorporate this into the wet mixture.

Fold in marshmallow bits and semi-sweet chocolate chips.

Optional: Chill the dough for up to 36 hours for better flavor.

Drop rounded balls of dough onto the baking sheets, spaced 2 inches apart.

Bake for 8 to 10 minutes until soft in the center. They should look slightly puffed.

Press extra chocolate chips and marshmallow bits into the tops immediately after baking.

Allow to cool for a few minutes, then transfer to a wire rack to cool completely.