In a large bowl, mix together the pumpkin puree, water, brown sugar, cocoa powder, vanilla extract, baking powder, baking soda, salt and cinnamon (everything except the vital wheat gluten). I like to use a whisk for this step to make sure everything is really well combined.
Once everything is well mixed, add in the vital wheat gluten and combine with a spatula. Mix as minimally as possible, just enough to combine everything. Over-mixing will result in a more chewy texture.
Roll the dough into balls and flatten them out a bit. Place them on a parchment paper lined baking sheet. You should end up with 20 cookies - they are about 2 tablespoons each.
Bake for 16 - 19 minutes.
While the cookies are baking, make the frosting. In a bowl, mix the avocado oil and powdered sugar together. I just use a fork until it reaches a frosting-like texture - think Oreo filling.
Once the cookies are baked, allow them to cool for at least 20 minutes.
Frost 10 of the cookies with the frosting, and place the remaining 10 cookies on top.