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

In a medium mixing bowl, use a fork to thoroughly mash the ripe bananas until mostly smooth.

Add the rolled oats, chia seeds, maple syrup, ground cinnamon, and optional vanilla extract to the bowl. Stir well until a cohesive dough forms.

If using optional add-ins like dark chocolate chips or chopped walnuts, gently fold them into the dough now.

Let the cookie mixture rest for 5 minutes to allow the chia seeds and oats to absorb the moisture.

Use a cookie scoop or spoon to drop mounds of dough onto the prepared baking sheet. Gently flatten and shape each mound into a rounded cookie shape.

Bake for 12 to 15 minutes, or until the edges are lightly golden and the bottoms are set.

Remove from the oven and let cool on the pan for 5 minutes before transferring the cookies to a wire rack to cool completely.