Mix the chicken with the soy sauce, rice wine, ginger, garlic and a pinch of salt in a large bowl. Put in the fridge and leave to marinate for at least 1 hr or ideally overnight. Meanwhile, make the sauce. Tip the rice wine, vinegar and sugar into a saucepan with a pinch of salt and bring to the boil. Stir until the sugar has dissolved, then add the garlic and ketchup. Continue to cook for 10 mins until syrupy, then remove from the heat and set aside. To prepare the toppings, put the coriander and spring onion in a bowl of iced water to perk them up. Toast the peppercorns in a dry frying pan, if using, then crush using a pestle and mortar. Mix with 1 tbsp sea salt and set aside.
Mix the beaten egg into the chicken mix, then stir in the cornflour and five-spice powder until the chicken is coated. Set aside. Pour the oil into a wok until it’s no more than a third full and heat to 170C, or heat a deep-fat fryer to the same temperature. If you don’t have a thermometer, drop a bit of the batter into the oil; when the batter sizzles and turns golden within 1 min, it’s ready. Fry the chicken in batches for 4-5 mins until golden and crisp, then drain on kitchen paper and keep warm in a low oven.
Meanwhile, gently reheat the sauce and add the soy sauce, stock pot or cube, vegetables, pineapple and ginger. Simmer for 3 mins until the veg is slightly softened. Mix the chicken with the sauce and serve with the coriander and spring onions, salt and pepper mix and some rice on the side.