Preheat the oven to 350°F (175°C). Line two baking sheets with parchment paper.
In a large bowl, cream together the softened butter, brown sugar, and granulated sugar until light and fluffy, about 2-3 minutes.
Add the egg and vanilla extract to the butter and sugar mixture, and beat until combined.
Stir in the mashed bananas until evenly incorporated.
In a separate bowl, whisk together the all-purpose flour, baking soda, salt, and ground cinnamon.
Gradually add the dry ingredients to the wet ingredients, mixing just until combined. Do not overmix.
Fold in the semisweet chocolate chips evenly throughout the dough.
Using a tablespoon or cookie scoop, drop rounded spoonfuls of dough onto the prepared baking sheets, spacing them about 2 inches apart.
Bake in the preheated oven for 10-12 minutes, or until the edges are lightly golden but the centers remain soft.
Remove from the oven and let the cookies cool on the baking sheets for 5 minutes before transferring them to a wire rack to cool completely.