In a saucepan over medium heat, melt 113 g of unsalted butter, stirring until it turns golden amber and releases a nutty aroma, about 5-7 minutes. Remove from heat and cool in the refrigerator for 10 minutes.

In a mixing bowl, mash 80 g of ripe banana with 1 tsp of ground cinnamon until chunky purée. Add cooled brown butter, 100 g light brown sugar, 50 g granulated sugar, and 0.5 tsp vanilla extract. Mix until smooth yet slightly chunky.

In a separate bowl, whisk together 130 g all-purpose flour, 60 g rolled oats, 0.5 tsp baking powder, 0.5 tsp baking soda, and 0.5 tsp salt. Fold this into the wet mixture gently until no flour streaks remain.

Add 130 g semi-sweet chocolate chips to the dough and fold them in gently until evenly distributed. Avoid overmixing to keep cookies light and chewy.

Cover the bowl with plastic wrap and chill dough in the refrigerator for at least 30 minutes, or up to 48 hours.

Preheat the oven to 350°F (175°C).

Using a cookie scoop, portion out rounded bits of dough onto a parchment-lined baking sheet, spacing about 2 inches apart.

Bake for 12-14 minutes, or until edges are golden brown. The aroma of banana and chocolate will fill the kitchen.

Let cookies rest for 5 minutes on the baking sheet before transferring to a wire rack to cool completely.