Pat the prawns dry with kitchen paper. Pour the vegetable oil into a wok or large pot so there's at least 5cm/2in of oil, then heat over a medium heat until it reaches 180°c/350°F. You can also use a deep fat fryer.

In a large bowl, add the prawns to the beaten egg whites and coat them well.

Add the cornflour gradually and mix thoroughly with your hands until the coating feels like a thin batter that just clings to the prawns. You may not need all 150g.

Once the oil is ready, add the coated prawns a few at a time and fry each batch for 3 to 4 minutes, turning regularly with a slotted spoon or tongs. Don't overcrowd the pan, as it drops the oil temperature.

Once the prawns are golden brown, lift them out onto kitchen paper to drain while you fry the remaining batches.

As the last batch fries, grind the garlic, chilli, salt and pepper together in a pestle and mortar. If you don't have one, use a bowl and the back of a spoon.

Heat a small frying pan over high heat, add the garlic and chilli mixture, and dry fry for 1 to 2 minutes to release the flavours.

Toss the crispy prawns with the garlic and chilli mix in a bowl, coating them thoroughly.

Serve hot with hot chilli oil or sweet chilli sauce.