Place the butter in a medium saucepan over medium heat. Cook, stirring or swirling the pan often, until the butter foams and the milk solids at the bottom turn golden brown. Once it develops a nutty aroma, remove it from the heat and allow it to cool for a few minutes.

Pour the browned butter into a large mixing bowl. Add the brown sugar and granulated sugar, then mix until combined.

Add the mashed banana, vanilla extract, and egg. Stir until the wet ingredients are well combined.

In a separate bowl, whisk together the all-purpose flour, baking soda, salt, and cinnamon.

Add the dry ingredients to the wet ingredients. Mix just until a cohesive cookie dough forms. Do not overmix.

Fold in the semisweet chocolate chips.

Cover the bowl and chill the cookie dough in the refrigerator for 30 minutes to 1 hour.

Preheat the oven to 350°F. Line a large baking sheet with parchment paper.

Use a cookie scoop or spoon to portion the chilled dough onto the prepared baking sheet, leaving space between each cookie.

Bake for 12 minutes or until the edges are set and the centers still look slightly soft.

Allow the cookies to rest on the baking sheet for 5 to 10 minutes. Transfer them to a wire rack to finish cooling.