Peel the prawns and discard the heads and shells. Cut an incision along the back of the prawn and pull out and discard the intestinal tract. Keep prawns refrigerated until ready to serve.

Use a knife to cut away the skin and pith of the grapefruit, then cut the fruit across into thin rounds.

Slice the chilli in half, discarding seeds, and finely chop. In a bowl, mix together the chilli, lime juice, fish sauce and sugar, stirring until the sugar has dissolved.

Cut the avocados in half, scoop out the flesh in one piece and slice thinly.

Arrange pieces of avocado alternately with slices of grapefruit and three prawns each on individual plates. Scatter with the coriander and mint leaves, pour over the dressing and drizzle with a little extra virgin olive oil.