Place the ginger, spring onion whites, onion and 500 ml (2 cups) of water in a saucepan and bring to the boil over high heat.
Add the chicken breasts and bring back to the boil, then cover and turn to the lowest heat to poach gently for 12-15 minutes until the chicken is cooked.
Pierce the chicken with a skewer – the juices should run clear.
Plunge the chicken into an ice bath to stop it cooking and set the poaching liquid aside.
To make the Sichuan sauce, combine the sauce ingredients in a bowl with the spring onion greens and 125 ml (½ cup) of the poaching liquid and set aside.
Shred the chicken (but not too finely) and pound with a rolling pin to make flat pieces.
Arrange the cucumber on two serving plates, then top with the chicken.
Pour over the sauce and serve.