In a medium bowl, combine flour, cocoa and baking soda; set aside.
Combine sugars in large bowl. Using an electric mixer blend in butter, scraping down the sides of the bowl. Add eggs and vanilla, and beat at medium speed until light and fluffy.
Add the flour mixture and the chocolate chips, blend at a low speed until combined. Batter will be stiff.
Gather about four marshmallows in the palm of your hand and cover them with a heaping tablespoon of dough. Wrap the cookie around the marshmallows, completely encasing them and forming a 2-inch-diameter dough ball.
Place cookies on ungreased cookie sheets, 2-inches apart. Bake 10- 12 minutes. Cool on pan for two minutes then transfer to cool flat surface.