Place the chicken in one layer in the bottom of a saucepan with enough water to cover by about 6cm. Add the spring onion, ginger, garlic and peppercorns. Bring to the boil and then immediately reduce the heat to low and gently simmer for 12-14 minutes (depending on the size of your chicken) and then remove from the heat. Cover and allow the chicken to sit in the poaching liquid for a further 10 minutes until the juices run clear and then remove and refresh in a bowl of water with ice (reserve a little of the poaching liquid). Leave to cool in the water.
Place the noodles in a bowl and pour over boiling water. Leave to sit for 10 minutes (or cook according to the packet instructions). Refresh in cold water, drain and allow to cool.
Make the peanut dressing. Place all the ingredients in a bowl and mix together. Whisk in 1-3 tbsp of poaching liquid (or water) until the dressing is smooth.
Drain the chicken and pat dry. Bash the meat with a rolling pin or the base of a pan to flatten and loosen the meat slightly and then shred into strips using two forks. Drizzle over a little of the peanut dressing and toss through.
Mix together the sesame oil, vinegar, soy sauce and sugar until the sugar dissolves. Add a squeeze of lime juice to taste. Pour over the noodles and toss through the coriander and mint.
Place the noodles on a large serving dish and arrange the cucumber on top. Arrange the chicken on top of the cucumber. Drizzle with more of the dressing, scatter with the sesame, chilli and spring onion. Serve with any remaining dressing on the side.
