Blend half the fish & prawn mix briefly in a food processor to form a rough paste. Remove & scrape out into a bowl. Add the remaining half of the chopped fish mix. Add the rest of the ingredients & mix gently.
Form into 4 nice, even, round shaped burgers. Place on a tray & chill in the fridge for 15-20 mins.
Mix the mayo & chilli sauce together in a small bowl, season & add the lime juice.
Heat the oil in a frying pan over a medium heat & fry the burgers for 3-4 mins each side or until they have a nice crust & the fish is cooked through.
Take your toasted buns and spread on a nice dollop of chilli mayo. Place the burger in each one. Top with the baby gem, cucumber ribbons, scallions & bun top.
Some homemade wedges would go really well with this.