First, preheat the oven to 350ºF and spray a baking sheet with nonstick cooking spray.
Next, combine melted butter and brown sugar until there are no lumps. Then, add mashed banana, egg, and peanut butter, and mix again.
Add salt, quick-cooking oats, baking soda, ground cinnamon and mix until everything is combined. Add in optional chocolate chips and mix again.
Refrigerate dough for 20 minutes to set.
Slightly wet your hands. Then, scoop 2 tablespoons of batter into your hands and form it into a ball. Place it onto the cookie sheet and slightly press down to form a cookie shape. The batter will feel a bit wet, but they will be so soft and chewy when done baking!
Repeat the process above until you've fit 6-8 cookies on your baking sheet.
Bake cookies at 350ºF for 11-14 minutes or until they begin to turn golden brown.
Remove cookies and let cool for a couple of minutes on the baking sheet before transferring to a wire rack to continue cooling for at least 20 minutes to firm up. Sprinkle on coarse sea salt and enjoy!