Line two baking sheets with parchment paper and set aside.
In a medium bowl, mix, using a hand mixer, the butter and brown sugar together until the mixture becomes light and sugar combines, will take up to 1 to 2 minutes. Now, add in the egg replacement and vanilla.
In another bowl mix together the flour, cocoa powder, baking soda, and salt.
Now, add the dry ingredients into the wet mixture, stirring until only combined. Gently fold in the marshmallows and chocolate chips.
Scoop even amounts of dough onto cookie sheets, leaving about 2 inches of space in between each ball of dough.
Bake for 10 minutes. Let cool on cookie sheet for 10 minutes before serving with a glass of milk!