Preheat the oven to 350 degrees. Line a baking sheet with parchment paper or a silicone mat.

Using a hand or stand mixer, cream together butter, brown sugar and granulated sugar for about 2 minutes. Add eggs and vanilla and mix until combined.

In a separate bowl, combine flour, cocoa powder, baking soda and salt. Add the dry ingredients to the butter mixture and mix on low until just combined. Don't overmix! Stir in the chocolate chips.

Using a 2 oz cookie scoop or a ¼ cup measure, scoop cookie dough balls and place 6 cookies at a time on the prepared baking sheet.

Bake for about 12 minutes. It is better to underbake than overbake! Transfer to a cooling rack to cool completely after cooling on the cookie sheet for 2-3 minutes.

Place the bag of mini marshmallows into a microwave safe bowl and microwave the marshmallows for 45 seconds to 1 minutes.

Remove the marshmallows and stir them and microwave for additional 15 second increments until fully melted.

Let the marshmallows cool slightly so that they aren’t too hot to the touch but not too long that they begin to harden. If they cooled too much, microwave again until melted.

Test the temperature first to make sure they aren’t too hot and then using both hands pinch a small amount of the melted marshmallow between two fingers.

Pull your fingers away from each other to create strands of marshmallows. Stretch these over each cookie, rubbing your fingers around the outside of the cookie to get the marshmallows to stick and separate from your fingers.

Repeat with each cookie and re-melt the marshmallows as necessary.