Tip everything out of the wok onto a plate and wipe the pan clean with some kitchen paper. Tip the sugar into the wok with 50ml water and boil until it turns a caramel colour. Measure out 300ml of warm water, then quickly tip it into the wok to stop the caramel colouring more. Add the ginger, vinegar, sesame oil and remaining soy sauce, and bring back to the boil. Return the chicken mixture to the wok, along with the peanuts or cashews, and continue to bubble for 20 25 minutes or until the sauce is reduced to a caramel consistency and coating the chicken.