Preheat the oven to 350°F (175°C).
In a large bowl, cream together the softened butter, brown sugar, and granulated sugar until smooth.
Add the mashed bananas and mix until well combined.
Beat in the egg and vanilla extract until fully incorporated.
In another bowl, whisk together the flour, baking soda, and salt.
Gradually add the dry ingredients to the wet mixture, mixing until just combined.
Fold in the chocolate chips.
Drop rounded tablespoons of dough onto a baking sheet lined with parchment paper.
Bake for 10-12 minutes, or until the edges are golden brown.
Allow cookies to cool on the baking sheet for a few minutes before transferring them to a wire rack to cool completely.