Preheat oven to 350°F. Prepare baking sheet with parchment paper or silicone baking mat.
In a large bowl, combine flour, salt, and baking powder and set aside.
In a stand mixer, cream together butter, sugar, and brown sugar. Mix until well combined, light and fluffy, about 1-2 minutes.
Add in hot cocoa mix and cocoa powder and mix on medium speed until well combined, scraping the sides of the bowl as needed.
Add in the eggs and vanilla extract and mix until well incorporated.
Mixing on low, add in the flour mixture a ½ cup at a time and mix until just combined. Do not over-mix.
Using a wooden spoon, gently combine the chocolate chips and Marshmallow bits until evenly mixed into the cookie dough.
Using a medium cookie scoop, drop about 1½ TBSP of cookie dough onto prepared cookie sheets. Space about 2 inches between cookies.
Bake about 9-11 minutes until cookies are set and edges appear slightly golden-brown.
Allow to rest for 2 minutes on the baking sheet prior to moving to a cooling rack to allow to cool completely.
Store in an airtight container for 5-7 days. Freeze extra to enjoy later!
