Soak the unshelled peanuts in hot water for ten minutes, then shell them. Heat 4 tablespoons oil in a wok and fry the peanuts until browned. Remove the peanuts and let cool (they will become crispier as they cool). Reserve the oil.
Mix 1 tablespoon Chinese cooking wine, salt, 1 teaspoon cornflour and fresh ginger and marinate the chicken for at least 30 minutes. In a separate bowl, mix the sugar, soy sauce, rice vinegar and 1 teaspoon cornflour.
Heat the reserved oil in the wok and add the Szechuan peppercorns, cooking until they become fragrant. Turn the heat to low and add the dried chillies, frying until they start to brown. Add the garlic and cook for a few seconds, then turn the heat back to high and add the chicken. Stir.
Add the other tablespoon Chinese cooking wine and the chilli powder and cook until the oil turns red. Mix in the sugar-rice vinegar paste and cook until the sauce is thickened. Add the peanuts and spring onion, stir for a few seconds then serve.