Step 1

Three hours before serving: make the dressing. Put the garlic and coriander in a food processor with 1 tsp salt and the sugar, then pulse to a pulp. Add the chilli, ginger and citrus juices and pulse until smooth. Cover and chill.

Step 2

Two hours before serving: cut the watermelon into segments, remove the skin and seed the flesh. Cut into lozenges about 3cm wide.

Step 3

Mix the melon and prawns and add the spring onions, lemongrass, ginger, lime zest and lime leaves. Chill.

Step 4

To serve: toss the dressing and herbs into the salad and scatter with chilli and peanuts.