Preheat oven to 350 F and line baking sheets with parchment paper.

In a medium sized bowl, whisk to combine the flour, cocoa powder, baking soda and salt. Set aside.

In the bowl of an electric mixer with the paddle attachment or with a handheld mixer on medium speed, cream the butter and sugars for 2-3 minutes, until creamy and pale. Scrape down the sides of the bowl with a spatula.

Add the eggs one at a time with the mixer on medium speed. Add the vanilla extract.

With the mixer on low speed, slowly add the dry ingredients and mix until just combined. Using a spatula or wooden spoon, stir in 3/4 cup of the chocolate chips.

Use a 1-ounce cookie scoop to drop the cookies onto the cookie sheet. Place them 3" apart. Top each cookie with a 4-5 extra chocolate chips.

Bake 9 minutes. Remove from oven and carefully stick 2-4 marshmallows on each cookie. Place sheet back in oven and bake another 1-2 minutes or until the center is just set. Let cool on the baking sheet for 10 minutes before then transferring them to a rack to cool.