Put the fish, zest of the lime, curry paste, coriander, garlic, chilli, egg and cornflour in a food processor and pulse until minced but not paste.
Scoop 3 tablespoons of mixture into your hand and form into a flattened cake shape. Repeat with the rest of the mixture.
Heat a tablespoon of oil over a medium high heat. Fry the fish cakes for 2-3 minutes on each side in batches.
Mix peanut butter, coconut milk, juice of the lime, soy sauce, fish sauce, chilli and brown sugar in a saucepan and melt over a medium heat. Set aside to cool. Serve the fish cakes with the sauce and sprinkled with sliced spring onion.
Nutrition information is an estimate and will vary depending on the exact ingredients used.