Preheat your oven to 350°F (175°C) and line a cookie sheet with parchment paper if desired.
In a mixing bowl, whisk together the flour, baking soda, baking powder, salt, and ground cinnamon. Set aside.
In another bowl, use an electric mixer or whisk to cream the softened butter and brown sugar together until light and fluffy.
Beat in the egg and vanilla extract, mixing until well combined.
Add the mashed bananas to the mixture and stir until combined.
Gradually add the dry ingredient mixture to the wet mixture, stirring until just combined. Be careful not to overmix.
If desired, fold in chocolate chips and chopped walnuts for added texture and flavor.
Drop tablespoon-sized portions of dough onto the prepared cookie sheet, spacing them about 2 inches apart.
Bake in the preheated oven for 10-12 minutes, or until the edges are golden and the centers look set.
Remove from the oven and let the cookies cool on the sheet for 5 minutes before transferring them to a cooling rack.