Mash the bananas with a fork, then add the flax seeds and cinnamon.
Peel the apple, then grate it with a cheese grater. Add to the banana pulp.
Finely chop the walnuts and add to the mash including the crumbs.
Add enough oats to create a malleable dough.
Let it rest until the oven warms up.
Turn the oven on to 170°C. Line a baking tray with parchment paper.
Make equal sized balls from the mixture and flatten these slightly between your palms.
Put the cookies on the lined baking tray and bake for about 15-20 minutes until golden brown.
Let them cool on a wire-rack.