Rinse the chicken under cold water, trim excess fat and remove the parson's nose; place the whole chicken in a large pot that fits it snugly.
Roughly chop 2 spring onions into 5 cm (2 in) pieces, add to the pot with 5 coriander sprigs, crushed ginger pieces and 1/4 tsp white peppercorns.
Cover the chicken with cold water, bring to a boil, then reduce heat and simmer very gently for 30 minutes; turn off heat and leave the chicken in the pot for 10 minutes more.
Remove the pot from heat and refrigerate until completely cool, then remove the chicken; reserve poaching liquid if desired and set the chicken aside.
Remove and shred leg and carcass meat; slice the white breast meat into thin slices and set aside separately.
Peel, seed and julienne the continental cucumber into ~10 cm pieces; lightly salt and drain for 10 minutes to remove excess water.
Finely slice the remaining spring onions, using mostly the white parts and a little green; pick coriander leaves and set aside for garnish.
To make the noodles, whisk 60 g mung bean flour with 300 g water until smooth, then pour quickly into a lightly greased 31 x 21 cm tray.
Steam the tray in a steamer for 20 minutes, then remove and cool to room temperature; turn the sheet onto a board and cut into pieces about 1 x 4 cm.
Toss the cut noodles with a few drops of vegetable or sesame oil to prevent sticking and refrigerate until ready to use.
Make the sesame paste by combining 4 tbsp tahini, 2 tbsp light soy sauce, 2 tsp fish sauce, 1 tsp sugar, 1 clove minced garlic, 1 tbsp lemon juice and 50 ml water; stir until smooth and add a little extra water if too thick.
Season shredded chicken with a pinch of salt and a few drops of sesame oil; separately toss noodles with a few drops of sesame oil and a little salt.
Arrange noodles on a serving platter, top with shredded leg meat and drained cucumber; drizzle about 3 tbsp of the sesame sauce over the chicken.
Sprinkle sliced spring onions, drizzle chilli oil, dust with ground Sichuan pepper and scatter coriander leaves over the dish.
Season sliced white breast meat with a little salt, arrange on top of the platter and serve.