First, preheat your oven to 350°F (175°C). While the oven is warming up, line your baking sheets with parchment paper or a silicone mat to prevent sticking.

Next, take a large mixing bowl and soften your butter. Add the brown sugar and granulated sugar to the bowl. Use an electric mixer or a hand whisk to cream them together until the mixture is light and fluffy this usually takes about 2 to 3 minutes.

Once that’s ready, crack in an egg and pour in the vanilla extract. Mix everything together until it’s well combined. Now, add your mashed bananas to the bowl and stir them in thoroughly.

In a separate bowl, whisk together all your dry ingredients: flour, baking soda, baking powder, salt, cinnamon, and nutmeg.

Slowly add the dry mixture to the wet banana mixture. Stir gently, just until everything comes together—you don’t want to overmix because that can make the cookies tough. Next, fold in the chocolate chips and walnuts if you’re using them.

Using a tablespoon or a cookie scoop, drop dollops of dough onto your prepared baking sheets. Make sure to leave about 2 inches of space between each cookie to give them room to spread.

Bake the cookies for 12 to 15 minutes. You’ll know they’re done when the edges turn golden brown and the centers look set.

Take the baking sheets out of the oven and let the cookies cool there for about 5 minutes. Then transfer them to a wire rack to cool completely.