In a medium bowl, whisk together the flour, baking powder, baking soda, and salt.
In a separate large bowl, beat the butter, granulated sugar, and brown sugar together until light and fluffy. Beat in the egg and vanilla extract.
Stir in the mashed bananas, vanilla wafer crumbs, and pecans.
Gradually add the dry ingredients to the wet ingredients and mix until just combined.
Cover the dough and chill for at least 30 minutes.
Preheat the oven to 350°F (175°C).
Line a baking sheet with parchment paper.
Use a cookie scoop or spoon to form the dough into balls and place them on the prepared baking sheet.
Bake for 12-15 minutes, or until the edges are golden brown.
Let the cookies cool on the baking sheet for 5 minutes before transferring them to a wire rack to cool completely. Enjoy!