First marinade the chicken by placing the diced thigh pieces in a bowl and sprinkling with the cornflour. Stir well then add the soy sauce and rice wine and stir again.
Heat the oil in a wok and the Sichuan peppercorns and chillies, fry for twenty seconds and then add the peanuts. Fry for two minutes.
Add the chicken and the leeks, stir fry for three to four minutes then add the garlic and ginger, mix well.
Pour in the Hoisin sauce and a splash of water and mix to coat the other ingredients. Cook for another two or three minutes until the thigh meat is cooked through.
Remove from the heat, garnish with spring onions and serve.