For the sauce
Put the cucumber matchsticks in a colander, sprinkle with the salt and cover with a plate with a weight on top. Set the colander in a bowl or on a deep plate to catch the drips, and leave to drain for 30 minutes.
Put the chicken portions in a large pan and just cover with water. Add 1 tablespoon of the soy sauce, the five-spice powder and the lemon juice, cover and bring to the boil. Reduce the heat and simmer for about 20 minutes.
Lift out the poached chicken with a slotted spoon, and leave until cool enough to handle. Remove and discard the skin. Bash the chicken lightly with a rolling pin to loosen the fibres. Slice into thin strips. Reserve.
Heat the oils in a large frying pan or wok. Add the sesame seeds, fry for 30 seconds, then stir in the remaining 3 tablespoons of soy sauce and the sherry. Add the carrots, and stir-fry for 2–3 minutes until just tender. Remove from the heat and reserve.
Rinse the cucumber well, pat dry with kitchen paper and put in a bowl. Add the spring onions, beansprouts, cooked carrots, pan juices and shredded chicken, and mix together. Transfer to a shallow dish. Cover and chill for about 1 hour, turning the mixture once or twice.
To make the sauce, cream the peanut butter with the lemon juice, sesame oil and chilli powder, adding a little hot water to form a paste, then stir in the spring onion.
Arrange the chicken mixture on a serving dish, and serve with the peanut sauce.