Preheat your oven to 350°F (175°C).
In a large mixing bowl, cream together the softened butter and brown sugar until light and fluffy.
Add the mashed bananas and mix until well combined.
Beat in the egg and vanilla extract until smooth.
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 chocolate chips if desired.
Use a tablespoon to scoop the dough onto a baking sheet lined with parchment paper.
Flatten the dough slightly and top with banana slices if using.
Bake in the preheated oven for 12-15 minutes or until the edges are golden brown.
Let the cookies cool on the baking sheet for 5 minutes before transferring to a wire rack to cool completely.