Preheat oven to 180°C
Whisk softened unsalted butter and mashed banana in a bowl till smooth. Add the cookie mix. Stir to form a soft dough.
Scoop tablespoon size cookie dough balls, 2 inches apart, on to a lined tray.
Bake for 12 minutes OR for 15 minutes if you prefer a crisper cookie.
Allow cookies to cool for 2 minutes before removing from the tray.