1) Lightly toast the pine nuts for 2-3 mins, in a frying pan, over a medium heat until golden. Remove and set to one side. 2) Put the borlotti beans into a large bowl and mash well. Add the pine nuts, onion, tomato paste, half the breadcrumbs, the thyme and egg. Season well, then mix together until thoroughly combined. 3) Shape the mixture into 4 burgers. Coat the outside of each burger with the remaining breadcrumbs. Cover and chill in the fridge for at least 30 mins. 4) To cook fry in the oil for 3-4 mins each side until golden. Drain on kitchen paper, then serve in toasted buns.