Mash the beans with a potato masher in a bowl until they are smooth, then add the pesto,
breadcrumbs, egg, a pinch of salt, and pepper to taste, and mix well.
Heat half the oil in a non-stick frying pan over a low heat and cook the onion and garlic until
soft. Add to the bean mixture and mix well.
Heat the remaining oil in the frying pan. Spoon in the bean mixture, in 6 separate mounds, then
press each one down with the back of a spoon to form a burger.
Cook the burgers for 4-5 minutes, then carefully turn over and cook for a further 4-5 minutes
Meanwhile, slice the rolls in half and smear each one with the hummus.
Remove the burgers from the frying pan and drain on kitchen paper. Place each one in a roll, top
with the tomatoes, cucumber and salad leaves and serve.