Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper.
In a mixing bowl, mash the ripe bananas until smooth. You should have about 1 cup.
In another bowl, cream together the softened butter, brown sugar, and granulated sugar until light and fluffy.
Add the mashed bananas, egg, and vanilla extract to the butter mixture and mix until combined.
In a separate bowl, whisk together the flour, baking soda, baking powder, salt, and ground cinnamon.
Gradually add the dry ingredients to the wet ingredients, mixing until just combined. Do not overmix.
If desired, fold in the chopped walnuts or chocolate chips.
Drop tablespoon-sized balls of dough onto the prepared baking sheet, spacing them about 2 inches apart.
Bake in the preheated oven for 10-12 minutes or until the edges are lightly golden and the tops are set.
Remove from the oven and let the cookies cool on the baking sheet for about 5 minutes before transferring them to a cooling rack to cool completely.