Place the beans in a large mixing bowl and roughly mash with a potato masher.
Add the sweetcorn, red onion, grated carrot and 2 tsp of the Cajun seasoning. Mix until well combined. Taste the mix and add salt and pepper to taste and add more Cajun seasoning if you wish, until it has a flavour and spiciness that you like.
Mix in the breadcrumbs, then add the egg bit by bit, until you have a mix that is bound, but not too wet to handle.
Shape the mix into 6 equal-sized burgers, about 2cm thick.
Place on a plate lined with greaseproof paper, cover and chill for 30 minutes, or until you are ready to cook them.
While the burgers chill, make your salsa by mixing all the ingredients together, season to taste with a little salt and pepper, cover and refrigerate until needed.
Spray a large non-stick frying pan with low-calorie cooking spray and place over a medium heat.
When hot, carefully add the burgers and fry for around 5 minutes until the underside is crisp and well browned, before carefully flipping. Cook for a further 5 minutes. Try not to keep flipping the burgers as the more they are handled, the more likely they are to fall apart. The burgers are cooked when they are well browned and piping hot in the middle.
You may find it easier to cook the burgers in 2 batches. The first batch can be placed on a tray and kept warm in a low oven while you cook the rest.
To serve, fill the wholemeal rolls with mixed salad leaves, place a burger on top and finish with a dollop of avocado salsa.