Preheat the oven to 350 degrees Fahrenheit and line a large baking sheet with parchment paper (or spray it with cooking oil).

Mash the banana into a mixing bowl until most of the chunks are out (it can be a little chunky just not overly chunky).

Add the peanut butter and oats and mix everything together until a sticky dough forms.

Use a spoon to drop the cookie dough onto the baking sheet, creating any size of cookie you like (note very small cookies will require less bake time). The cookies won’t spread, so form them into the shape you want them to be in - I stick with round mounds.

Bake the cookies for 10 to 12 minutes, or until they are slightly golden-brown around the edges.

Allow the cookies to cool for at least 15 minutes before using a spatula to remove them from the baking sheet to serve.