Preheat oven to 325° and line a baking sheet with parchment paper.
In a large bowl, cream together the butter and sugar until light and fluffy.
Next, add in the eggs and combine until well combined.
In a medium bowl, whisk together the flour, cocoa powder, baking soda, baking powder and salt.
In thirds, add the flour mixture to the butter mixture until well combined.
Using a medium size cookie scoop, place cookie dough onto the baking sheet.
Dip your thumb in water or spray with non-stick baking spray and create a “well” on the top of the cookies. Place 2-4 marshmallows into this well.
Bake for 8-10 minutes until the center has just set.
Top with extra marshmallows and chocolate morsels while the cookies are still warm. Allow to cool at room temperature before serving.