If using live/raw prawns, bring a pan of well-salted (or sea) water to the boil and blanch the prawns for about 30 seconds. Leave to cool and peel.
Wrap each prawn in a piece of sea lettuce and thread onto cocktail sticks, interspersed with lengths of spring onion. (Aim for three medium or two large prawns per stick).
Make the batter by mixing all the ingredients together, adding more water if necessary to bring it to the consistency of thick paint (do not worry if it has lumps in it).
Make the dipping sauce by mixing the soy sauce and rice wine vinegar together and adding the chopped spring onions.
Heat the oil in a pan, then dip the cocktail sticks 3-4 at a time in the batter and drop straight into the oil. Fry until crisp (about 1 minute), drain briefly on kitchen paper, sprinkle with salt and serve immediately.
Eat by picking up the sticks by the long end, dipping in the sauce, and eating in your fingers off the stick.