Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper.

In a large mixing bowl, combine the softened butter, granulated sugar, and brown sugar. Cream until light and fluffy, about 2 to 3 minutes.

Add the mashed ripe bananas to the butter and sugar mix, stirring until fully incorporated.

Crack the egg into the bowl and pour in the vanilla extract, mixing until well combined.

In a separate bowl, whisk together the flour, baking soda, salt, and ground cinnamon. Gradually add this mix to the wet ingredients.

Gently combine the wet and dry mixtures, ensuring not to overmix.

Fold in oats, and add desired chocolate chips or chopped walnuts.

Drop tablespoons of cookie dough onto the baking sheet, leaving space between each.

Bake in the oven for 10 to 12 minutes until lightly golden around the edges.

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