Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper.
In a medium bowl, whisk together the flour, baking powder, baking soda, salt, and cinnamon. Set aside.
In a large mixing bowl, cream the butter, brown sugar, and granulated sugar until light and fluffy.
Beat in the egg and vanilla extract, then mix in the mashed bananas until fully incorporated.
Gradually add the dry ingredients to the wet ingredients, mixing until just combined.
Fold in chocolate chips or walnuts if using.
Drop tablespoon-sized portions of dough onto the prepared baking sheet, spacing them about 2 inches apart.
Bake for 10-12 minutes, or until the edges are golden brown and the cookies are set.
Let cool on the baking sheet for a few minutes before transferring to a wire rack to cool completely.
Top with glace icing and sliced bananas if you wish.
