Preheat oven to 325°F. Line a baking sheet with parchment paper or a silpat mat.
In a large bowl, add peeled banana. Using a sturdy whisk or fork, mash until smooth. Add the remaining wet ingredients: peanut butter, maple syrup, coconut oil, flax egg, and vanilla. Whisk until well incorporated.
Add the dry ingredients: oats, cacao powder, baking soda, baking powder, and cinnamon. Using a rubber spatula, stir and fold until well mixed. Fold in chocolate chips and walnuts.
Using a cookie scoop, scoop and drop cookie dough on the prepared pan. Flatten slightly, as they won’t spread much during baking. Bake for 10-13 minutes and allow it to cool on the pan for 20 minutes to help it set more. Carefully lift cookies and place on a cooling rack to cool completely. Store in an airtight container or ziploc on the counter or in the refrigerator for up to a week.
Enjoy!
(Recipe adapted from Beaming Baker)