Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper.
In a large mixing bowl, cream together the butter, granulated sugar, and brown sugar until light and fluffy.
Beat in the egg and vanilla extract until well combined.
Add the mashed bananas to the mixture and mix until fully incorporated.
In a separate bowl, whisk together the flour, baking soda, salt, cinnamon, and nutmeg.
Gradually add the dry ingredients to the wet ingredients, mixing until just combined.
Stir in the rolled oats, walnuts, and chocolate chips, if using.
Drop rounded tablespoons of dough onto the prepared baking sheet, spacing them about 2 inches apart.
Bake for 12-15 minutes, or until the edges are golden brown and the centers are set.
Allow the cookies to cool on the baking sheet for a few minutes before transferring them to a wire rack to cool completely.
Variations & Tips
For a different twist, you can substitute the walnuts with pecans or almonds. If you prefer a sweeter cookie, consider adding a drizzle of icing made from powdered sugar and a touch of milk. To make these cookies gluten-free, use a gluten-free flour blend in place of the all-purpose flour and ensure your oats are certified gluten-free. Feel free to play around with different mix-ins such as dried cranberries or white chocolate chips to create your own unique version of these banana bread cookies.
