Preheat oven to 350 degrees and line a metal cookie sheet with parchment paper.

In a large microwave-safe bowl, add butter and chocolate chips.

Melt in the microwave for 30 seconds, being careful not to burn the chocolate chips. Add 10 seconds at a time until all of the chocolate is melted. Let cool for 3 minutes.

Add sugar to chocolate and mix until smooth. Add egg one at a time and mix with each one. 

Add vanilla extract and mix. 

In a small bowl, add flour, hot chocolate mix, baking powder, baking soda, and salt and whisk until combined.

Add the flour mixture to the chocolate mixture and mix just until all the flour is incorporated. Let the batter sit for about five minutes to let it absorb the flour. Fold in marshmallows and chocolate chips. 

Scoop batter onto a cookie sheet and bake for 10 minutes. 

Remove from oven and add a few mini marshmallows on top to make the cookies look prettier.

After about 10 minutes, move the cookies over to a wire rack to cool.