Put chicken breast, sliced ginger, and the white part of the scallions into a saucepan. Add water that’s enough to cover the meat.
Bring water to a boil then turn down the heat to a bare simmer. Cover with a lid. Leave to cook for 8 minutes. Then turn off the heat and let it sit (covered) for a further 3 minutes (see note 2).
Take out the chicken (keep the cooking liquid) and transfer it to a large bowl of cold water, with ice cubes if available. Once cooled completely, drain then pat dry the surface of the meat with kitchen paper.
Tear the chicken into strips with your hands (Or, follow the traditional method of hammering the chicken with a rolling pin to loosen it up before shredding it).
In a bowl, mix all the seasonings (light soy sauce, black rice vinegar, chili oil, sesame oil, ground Sichuan pepper, salt, and sugar) with 2 tablespoons of the chicken cooking liquid.
Place julienned cucumber on the serving plate. Top with shredded chicken. Pour the sauce mixture over. Garnish with finely chopped scallion greens and toasted sesame seeds.
Notes
1. You may replace chicken breast with boneless chicken thigh which taste more tender and flavorful.2. If you’re poaching more than 1 chicken breast at a time, you’ll need to increase the cooking and resting time. If unsure, poke a kitchen thermometer into the middle of the thickest part of the chicken, the temperature should read above 165°F/74°C.