Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper.
In a mixing bowl, combine the softened butter and brown sugar, and cream them together until light and fluffy.
Add the mashed bananas, egg, and vanilla extract to the butter mixture, and mix until well combined.
In another bowl, whisk together the flour, baking soda, and salt. Gradually add the dry ingredients to the wet mixture, stirring until just combined.
Fold in the chocolate chips and walnuts (if using).
Using a tablespoon, drop rounded spoonfuls of cookie dough onto the prepared baking sheet, leaving space between each for spreading.
Bake in the preheated oven for 10-12 minutes, or until the edges are golden but the centers appear soft.
Remove from the oven and allow the cookies to cool on the baking sheet for 5 minutes before transferring them to a wire rack to cool completely.
Notes
Serve the cookies warm, piled high on a beautiful plate, and dusted lightly with powdered sugar for an extra touch of sweetness. Enjoy with a glass of milk!