Vietnamese salad of grilled prawns with papaya

INGREDIENTS
12 large raw prawns
2 tbsp vegetable oil
1 tsp rice wine vinegar
1 tsp sugar
1 red chilli, deseeded and very finely chopped
2 garlic cloves, crushed
2 tbsp Vietnamese fish sauce or Thai fish sauce, such as nam pla
1 tbsp lime juice
1 tbsp chopped rau ram (Vietnamese mint)
or mint leaves, plus extra sprigs to garnish
1 green papaya, deseeded, quartered
lengthways, and thinly sliced
1⁄2 cucumber, deseeded and cut into thin strips

METHOD
Peel and devein the prawns, removing and discarding the heads and tails. Spread them out on a foil-lined grill rack, brush with the oil, and grill for 2–3 minutes, or until they turn pink.
Meanwhile, whisk the rice wine vinegar, sugar, chilli, garlic, fish sauce, lime juice, and 75ml (21⁄2fl oz) cold water together in a bowl until the sugar dissolves. Add the cooked prawns to the bowl and stir well until they are coated in the dressing. Leave to cool completely.
Add the chopped mint, papaya, and cucumber and toss together. Transfer the salad to a serving platter, with the prawns on the top, and garnish with mint sprigs.