Whizz up one slice of bread to make breadcrumbs.
Peel and chop 2-3 sweet potatoes and put in a bowl with a splash of water, cover with clingfilm, pierce and microwave for 3 mins.
Meanwhile chop and fry a small onion/shalotte and add a tin of kidney beans for the last couple of mins. Whizz up in a blender until coarsley chopped.
Mash the sweet potato, mix in the onion and beans and a thick slice of cheese or two cut into tiny cubes. mould into little burgers - probably makes 10-12 burgers.
Cover in breadcrumbs and fry in oil/butter for a few mins each side until browned and crispy.
I have frozen some before cooking so will let you know what they are like when I defrost and cook them.