Thinly slice half the onion and set aside. Finely chop remaining onion. Heat oils in a wok over medium-high heat, then add chopped onion, oils, lemongrass, chilli, garlic, ginger and lime leaves. Stir-fry for 1 minute until fragrant. Add mince and stir-fry for 5 minutes or until almost cooked. Add sauces, lime juice and sugar, then stir-fry for a further minute until chicken is cooked through and sauce is reduced. Stir through sliced onion and herbs. Transfer to a platter and serve with the remaining ingredients, scooping chicken mixture into lettuce or onto wonton wrappers.