Place mince in a bowl, season well with salt and freshly ground black pepper. Shape mixture into four large patties. Coat patties in combined flour and cajun seasoning; discard excess flour mixture.

Heat oil in a large non-stick frying pan; add patties, cook until browned on both sides and cooked through.

Meanwhile, combine tomato, onion, and salt to taste in a medium bowl.

Cut turkish bread into four pieces; split pieces in half. Toast, cut-side up, under pre-heated grill.

Layer four toasted bread bases with lettuce, avocado and patties, then mayonnaise and tomato mixture. Top with sweet chilli sauce and remaining bread slices.