Mash banana in stand mixer or with hand mixer. Add egg, parsley, honey and salt and beat until combined. Fold in peanut butter with spatula.
Add in oats and flour and stir with wooden spoon, or gently combine with dough hook of stand mixer (stopping to scrape sides as necessary). Form ball.
Preheat oven to 300 degrees Fahrenheit. Grease 2 large cookie sheets with cooking spray.
Flour working surface and separate ball into halves. Turn one half out with rolling pin until approximately 1/4 inch thick. Use cookie cutter of choice to cutout dough. Place on greased cookie sheet.
Repeat by adding more dough to scraps, re-rolling, and cutting out cookies. Once all dough is used, place cookie sheets in oven to bake. Bake for about 40 minutes, flipping biscuits halfway through.
Once lightly browned on both sides, remove and let cool on wire rack.
Recipe Notes
Biscuits will harden more after they cool, so be careful not to over-bake.
Store half in cookie jar, and the rest in Ziploc bag in fridge to keep fresh. You can store in freezer bag in freezer if they need to last longer than a few weeks.