Preheat the oven to 350°F (180°C). Line a cookie sheet with parchment paper. Slightly oil paper with coconut oil. Set aside.
In a large bowl, mix mashed banana, peanut butter, vanilla, and maple syrup, if used.
Stir in oats, cinnamon, and chocolate chips.
Fold in blueberries and stir gently to avoid breaking the berries.
Use an ice cream scoop to form 6 cookie dough balls. If you used rolled oats, the batter is not sticking as well together as if you use instant oats, so make sure you wet your hands to pack the cookie batter.
Place the cookie batter on the baking sheet, and use a wet hand to press down the ingredients in a round cookie shape.
Bake in the center rack of the oven for 15-20 minutes or until the sides are golden brown.
Cool the cookies down 10 minutes on the cookie sheet, don't touch the cookies, they firm up as they cool down.
Gently slide a spatula under the cookies and transfer them to a cooling rack to firm up completely.
Store cookies in a cookie jar in the fridge for up to 3-4 days. Freeze in zip-lock bags for up to 3 months.