Step 1

Place the rice vermicelli in a bowl and cover with boiling water. Soak for about 5 minutes.

Step 2

Place rice vinegar and caster sugar in a small pan over medium heat. Bring to the boil, stirring to dissolve sugar, then remove pan from the heat and set aside.

Step 3

In a mortar and pestle, smash garlic clove and one third of the chilli into a rough paste, then add to sugar and vinegar mixture in the pan. When mixture has cooled, add fish sauce and lime juice, tasting as you go. It should taste quite zingy, a little sweet and salty.

Step 4

Drain the rice vermicelli and rinse under cold water. Run your fingers through them to ensure they're not stuck together, then place in a large bowl. Peel cucumber, halve lengthways and remove seeds. Finely slice and add to the noodles with the remaining chilli, herbs and prawns.

Step 5

Toss and divide among 4 plates. Pour dressing over salad, toss again and sprinkle with toasted cashews.