Poach the chicken breasts: place the chicken breasts in a pot large enough so they’re sitting on the bottom of the pot; pour in just enough water to cover the chicken pieces; add the knob of peeled, pounded ginger; bring the water to a boil, then immediately reduce the heat to low, and simmer until when you poke a thermometer into the widest part of the breast the internal temperature reaches 70°C (158°F). Remove and when the breasts are cool enough to touch, shred the chicken pieces into chunky strips using two forks or your hands.
Make the dressing while the chicken is poaching: to a jar with lid, add the two tablespoons of Chinese sesame paste, a teaspoon each of salt and caster sugar, two tablespoons each of light soy sauce, Chinkiang vinegar and sesame oil, half a teaspoon of ground roasted Sichuan peppercorns (or chilli flakes if you can’t source them), four tablespoons of Sichuan chilli oil and two tablespoons of sediment from the jar. Stir vigorously until well combined.
On a large serving plate, lay down a bed of torn lettuce leaves, followed by a layer of the cucumber slices.
To a large salad bowl, add the shredded chicken, grated cucumber, grated fresh ginger, half the thinly sliced scallions/spring onions, a tablespoon of sesame seeds, and half the dressing and combine well.
Spread the shredded chicken salad over the lettuce and cucumber, evenly pour the remaining dressing over the salad, sprinkle on the remaining thinly sliced scallions/spring onions and sesame seeds, along with the fresh coriander sprigs, and serve immediately.