In a large bowl or stand mixer cream butter and sugars. Add eggs one at a time until blended. Add vanilla and mix until light and creamy.
In a seperate bowl combine flour, cocoa, baking soda and salt. Add 1/3 cup of flour mixture to the butter/egg mixture at a time, mixing on low or stirring to combine. Mixture will be very thick.
Stir in chocolate chips, coconut and nuts until combined. Drop by rounded tablespoons onto parchment paper covered baking sheets.
Cook for 5 minutes remove from oven. Gently add 4-5 mini marshmallows to the tops of each cookie. You can press in ever so slightly to get them to stay on top. Return cookies to oven and bake for additional 4 minutes. Remove from oven and cool for 10 minutes before removing from cookie sheets.
Work in small batches so that you have time to add the marshmallow quickly.