In the bowl of a stand mixer beat your butter until soft and airy. Add your sugar and brown sugar and beat until combined. Add your eggs and vanilla and mix until combined.
In a small bowl combine your flour, baking soda, salt, coco powder. Add your flour mixture to your butter mixture slowly until combined.
using a large cookie scoop, roll out your cookies into balls. you should get about 24 cookies.
Flatten each ball and place about 3 chocolate chunks in the center of each. roll the dough back into a ball (stuffing the center of the ball with chocolate).
place your cookies on a cookie sheet with parchment paper, leaving about 2 inches of space between each cookie.
On the counter, Using the palms of your hand squish down each marshmallow down until it flattens. place one marshmallow on top of each cookie, slightly pressing down each cookie.
Place cookies in the fridge for at least 30 minutes
Bake your cookies at 375 degrees for 12 minutes. Let cool and enjoy!