1. Add the flour,potato starch,baking powder and salt to a large bowl. Whisk in the reserved kimchi liquid and one cup of water to make a smooth batter. Fold in the chopped kimchi and half the spring onion. The batter should have the consistency of a thick pancake batter;add another 50 millilitres of water if it's too stiff.
2. For the sauce,combine all the ingredients in a small bowl.
3. Preheat a couple of centimetres of oil in large,flat-based frying pan until about 170C. Test the temperature by dropping a little batter in the oil;it's ready if it fizzes immediately.
4. Using about two tablespoons of batter for each fritter,cook three or four at a time for 2½ minutes on one side. Sprinkle a little spring onion and sesame seeds on the uncooked sides and then flip and cook for another minute. Drain well on paper towel and repeat.
5. Serve the pancakes with the lettuce cups,sauce and coriander on the side. Dip the cakes in the sauce,then wrap in the lettuce with a sprig of coriander and eat.
Tips
1. Pick slender young spring onions,they have a finer flavour and are much more tender than mature ones.
2. Halve the lettuce,cut out the core and soak in cold water to make it easy to separate the cups.
3. Make sure that the oil comes back to temperature before starting the next batch of pancakes.