Put the vinegar and sugar into a small pan. Heat gently until the sugar has dissolved. Bring to the boil and boil rapidly for 6-7 minuts until a thin syrup is formed. Pour into a bowl and leave to cool. Cut the carrot and cucumber into thin strips. Mix with the onion and chilli. add the cooled syrup and mix well. Set aside. When ready to serve, add the peanuts and mix through.
Chop the salmon and prawns into little cubes.
Put the garlic, spring onion, chilli, lemongrass, coriander and fish sauce into a little blender and whizz to a rough paste.
In a large bowl, put the flour, eggs, paste and salt and pepper and beat to a thick batter. Add the fish and prawns and mix through.
Heat 4-6 tbsp groundnut oil in a large non-stick frying pan until very hot. Drop dessertspoonfuls of the mixture into the pan and fry for a few minutes each side until golden and cooked through. Drain on kitchen paper and serve with the fresh pickle.