Coat prawns lightly with corn flour, then deep-fry in hot oil until golden and crispy. Drain from oil.
Heat wok with 3 tablespoons oil, fry star anise, cloves and cinnamon stick until fragrant, then discard star anise, cloves and cinnamon stick, leaving only the fragrant oil in the wok. Add ginger and garlic and fry until golden. Stir in sauce ingredients and simmer until it turns rather thick. Add the prawns and stir-fry until they are well coated with sauce.
Dish out and garnish with spring onion curls and serve immediately.