Can also be substitued with beans or chickpeas.I very rarely do not have carrots and onions in so if I have nothing else I fall back on carrot and lentil burgers- chop up carrot and onion, boil lentils and cook carrot and onion (you are meant to cook them in oil separately but I am often lazy and chuck them in with the lentils ), mash it all together with seasoning, fresh parsley and any other herb