Place the ginger, spring onion whites, onion and 500ml of water in a saucepan and bring to a boil over high heat.
Add the chicken breasts and bring back to the boil. Cover and simmer gently for 11-14 minutes until the chicken is cooked.
Plunge the chicken into an ice bath to stop the cooking.
Set aside the poaching liquid.
Combine the Sichuan sauce ingredients in a bowl with the spring onion greens and 125ml of the poaching liquid.
Shred the cooked chicken and pound it flat with a rolling pin.
Arrange the sliced cucumber on serving plates, top with the chicken, and pour over the Sichuan sauce before serving.