Preheat the oven: Preheat your oven to 350°F and line a baking sheet with parchment paper so the cookies don't stick as they bake.

Mash the bananas: In a large bowl, mash the ripe bananas with a fork until mostly smooth, leaving just a few small lumps for texture.

Mix in oats and spices: Stir the rolled oats, cinnamon, vanilla extract and salt into the mashed banana until the oats are fully coated and the mixture looks thick and sticky.

Fold in mix-ins: Add the mini chocolate chips and walnuts, if using, and fold them in gently until evenly distributed through the dough.

Rest the dough: Let the dough sit for 5 to 10 minutes so the oats can soften and absorb some of the banana's moisture, giving the cookies a chewier texture.

Scoop the cookies: Drop rounded tablespoons of dough onto the prepared baking sheet, spacing them about 1 inch apart since they won't spread much.

Flatten slightly: Use the back of a spoon to flatten each mound to about 1/2 inch thick, since the dough holds its shape during baking.

Bake until golden: Bake for 15 to 18 minutes, until the edges turn light golden and the tops feel firm when touched.

Cool on the sheet: Let the cookies cool on the baking sheet for 5 minutes before transferring them to a wire rack, since they firm up as they cool.

Store or serve: Serve the cookies warm or let them cool completely before storing in an airtight container.