Preheat oven to 350 degrees Fahrenheit and line a baking sheet with parchment paper.
In a small bowl combine ground flaxseed (or egg replacer) and water. Let sit for 2-5 minutes before adding to recipe.
In a medium bowl combine gluten free flour, cinnamon, baking soda, and salt and whisk to combine.
In a large bowl beat sugars, softened butter, and flax egg until fluffy.
Add dry ingredients to wet a little at a time and mix until combined. Fold in vegan chocolate chips and marshmallows. (Optional: cover dough with plastic wrap and place in the fridge for 10-30 minutes to firm up)
Form dough into 1" balls and place about 2" apart on the baking sheet. Bake for 10-12 minutes, until edges are golden brown. The middle of the cookies will still be soft. Pro Tip: try to make sure the marshmallows end up in the center/on the top and not the sides of the cookie.
Remove from oven and let cool on baking sheet for 5 minutes before transferring to a wire rack to cool completely. Repeat for remaining dough.
Store leftover cookies (if there are any) in an airtight container for up to 4 days.