Shell the prawns, leaving the tails intact. Cut a slit along the back of each prawn and remove vein. Toss the prawns into seasoning (A) and marinate for 10 minutes.
Heat oil and sesame oil in a wok. Add dried chillies, garlic and ginger and fry until garlic and ginger are golden and chillies turn dark.
Add the prawns and toss for a few seconds before adding sauce ingredients (B) and bring to the boil. Add onion and spring onion and toss till heated through. Stir in corn flour mixture. Add coriander leaves then transfer to a serving dish.