1. Prepare the prawns – using a sharp knife, carefully cut out any black vein you may find running along the back of the prawn. Alternately you could get it done by your fishmonger.
2. Wash the prawns under cold running water and dry on a clean cloth, place them on a plate, cover with cling film and store in the fridge until required.
3. Make the chilli mayonnaise and store in the fridge until required.
4. Finely shred the spring onions.
5. De-seed and cut the chilli into fine julienne.
6. Place the flour onto a shallow tray and season with sea salt and freshly milled black pepper.
7. Make the tempura batter.
8. Heat the oil in a wok or deep saucepan to about 170°C (Gas Mark 3).
9. Toss the prawns through the seasoned flour and lower into the tempura batter.
10. When the oil is at temperature, carefully lift the king prawns out of the tempura batter and lower them into the oil.
11. Fry the king prawns for about 3 minutes, until they are crispy and light golden in color.
12. Using a slotted spoon, remove the king prawns from the oil and drain them on kitchen paper to remove any excess oil.
13. Serve the king prawns in tempura batter on a warmed plate with a small bowl of chilli mayonnaise.
14. Garnish with shredded spring onion and a few julienne of red pepper.