01 - Preheat the oven to 350°F. Line a baking sheet with parchment paper.
02 - In a large bowl, beat the softened butter, brown sugar, and granulated sugar together until light and creamy.
03 - Mix in the mashed bananas, egg, and vanilla extract until well combined.
04 - In a separate bowl, whisk together the rolled oats, flour, baking soda, cinnamon, and salt.
05 - Gradually add the dry ingredients to the wet mixture, stirring until just combined. Fold in chocolate chips or walnuts if using.
06 - Drop tablespoon-sized portions of dough onto the prepared baking sheet, spacing about 2 inches apart. Bake for 10–12 minutes or until the edges are golden but the centers remain soft.
07 - Let the cookies cool on the baking sheet for 5 minutes before transferring to a wire rack to cool completely.