With a potato masher or a fork, mash the banana into a chunky purée. Stir the oats with the banana, keeping in mind that the amount may vary depending on the size of the banana, but the result should not be too moist, so err on the side of extra oats.
1 banana, 50 g oatmeal or rolled oats
Cover a baking sheet with parchment paper and drop the cookies down with a spoon. If you care for perfect looks, use a glass to gently nudge the dough into a round shape.
Gently press any toppings you might want to add on top of the cookies, then transfer the baking sheet to the freezer for 5/10 minutes.
optional toppings (chocolate chips, walnuts, raisins, cranberries...)
Preheat the oven to 365°F. Transfer the baking sheet with the cookies in the preheated oven.
Bake the cookies for 15 minutes, then take them out and gently remove them from the baking paper with the help of a spatula.
Eat your delicious, healthy two-ingredient cookies right away, or keep them in a tin box and quickly warm them up in the oven or toaster before serving.